Montgomery Mutual Insurance v. Chesson

HOTTEN, J. At the heart of this case is whether the theories and methodologies of Ritchie Shoemaker, M.D. (“Dr. Shoemaker”) are generally accepted in the relevant scientific community. Namely, we must determine whether the Circuit Court for Howard County was correct in concluding that: (1) the differential diagnosis performed by Dr. Shoemaker was reliable and acceptable to establish general and specific causation, and (2) the differential diagnosis method is generally accepted in the medical community. 1 For the reasons that follow, we reverse the judgment of the circuit court. BACKGROUND Appellees, Josephine Chesson, Martha Knight, Carole Silberhorn, Linda Gamble, Kenneth Lyons, and Connie Collins, were employees of the Baltimore Washington Conference of the United Methodist Church (“BWCUMC”), located at 9720 Patuxent Woods Parkway, Columbia, Maryland.

In late 2002, several employees complained that there was an odor emanating throughout the walls of the facility. A maintenance crew investigated the situation and discovered mold in the walls. Two types of mold were found: Aspergillus and Stachybotrys. As a result of the exposure, each appellee filed a claim against BWCUMC and its insurer, appellant, Montgomery Mutual Insurance Company, with the Maryland Worker’s Compensation Commission (“the Commission”).

The claims alleged that appellees suffered an accidental injury or occupational disease, known as sick building syndrome, as a result of the exposure. A hearing was held and the Commission disallowed two of ⁵⁷² appellees’ claims and awarded the remaining appellees partial compensation. 2 Each appellee noted an appeal and the cases were consolidated. Before trial, appellant filed a motion in limine to preclude the testimony of Dr. Shoemaker. Appellant argued that Dr. Shoemaker’s testimony should be excluded because his methodologies and theories regarding the causal nexus between exposure to mold and human health effects were not generally accepted in the relevant scientific community.

Recognizing that Dr. Shoemaker was a board certified physician, who devoted a significant portion of his practice to caring for individuals who were exposed to water damaged buildings, the court denied the motion. The court then noted that a Frye-Reed hearing was unnecessary. The Commission’s decisions were subsequently reversed and appellant noted an appeal. Among other things, on appeal, appellant argued that the circuit court committed error by not conducting a Fryer-Reed hearing.

Montgomery Mut. Ins. Co. v. Chesson, 170 Md.App. 551, 556 , 907 A.2d 873 (2006). We held that the court correctly declined to conduct a Frye-Reed hearing because Dr. Shoemaker performed “certain tests” that were “not so unorthodox that would warrant subjecting them to a Frye-Reed analysis____” Id. at 569 , 907 A.2d 873 .

Specifically, we noted that a hearing was unnecessary because “expert opinions concerning the cause or origin of an individual’s condition are not subject to Frye-Reed analysis.” Id. An appeal was noted and a petition for certiorari was granted. See Montgomery Mut. Ins.

Co. v. Chesson, 396 Md. 12 , 912 A.2d 648 (2006). In reversing our decision, the Court of Appeals held that a Frye-Reed hearing should have been held “to determine whether the medical community generally ⁵⁷³ accepts the theory that mold exposure causes the illnesses that [appellees] claimed to have suffered, and the propriety of the tests Dr. Shoemaker employed to reach his medical conclusions.” Montgomery Mut. Ins. Co. v. Chesson, 399 Md. 314, 328 , 923 A.2d 939 (2007).

Noting that Dr. Shoemaker’s testimony involved more than generally accepted medical opinion and diagnosis, the Court explained that “Dr. Shoemaker employs medical tests to reach a conclusion that is not so widely accepted as to be subject to judicial notice of reliability.” Id. at 332 , 923 A.2d 939 (footnote omitted). Indeed, because “Dr. Shoemaker’s testimony was based on scientific opinion regarding the causal link between mold exposure and sick building syndrome ...,” the Court of Appeals reasoned that “his theories regarding causation and the tests he employed to diagnose [appellees] were subject to Fry e-Reed analysis.” Id. at 329 , 923 A.2d 939 . Accordingly, the case was remanded for the limited purpose of determining “whether Dr. Shoemaker’s methodologies used for diagnosis and theories regarding the causal connection between mold exposure and certain human health effects are generally accepted in the scientific community.” Id. at 336 , 923 A.2d 939 . At the Frye-Reed hearing, Dr. Shoemaker explained the genesis of his theories and methodologies.

Dr. Shoemaker began a rural family practice in Pocomoke City in 1980. Around 1997, some of his patients began developing acute and chronic symptoms from exposure to the Pocomoke River, and tributaries adjacent to the Chesapeake Bay. One of the symptoms, diarrhea, was treated with Cholestyramine, a drug approved by the United States Food and Drug Administration for treatment of elevated cholesterol. Cholestyramine was prescribed because it was commonly used “in primary care medicine to treat secretory diarrhea.” As Dr. Shoemaker expected, the diarrhea reduced; but surprisingly, there was an improvement concerning issues associated with memory, headaches, coughing, and muscle aches.

Based on this, Dr. Shoemaker published a paper in the Maryland Medical Journal reviewing other cases in which patients suffered memory loss, cognitive impairments, headaches, rashes, abdominal pain, di ⁵⁷⁴ arrhea, redness of the eyes, and bronchial spasms that were caused by exposure to the Pocomoke River. Soon thereafter, the Maryland Department of Health and Mental Hygiene appointed a committee to examine some of Dr. Shoemaker’s patients. The Center for Disease Control Prevention (“CDC”) worked with the committee and developed a case definition for the illness: Possible Estuary-Associated Syndrome (“PEAS”). 3 In diagnosing patients that purportedly had PEAS, Dr. Shoemaker would review possible exposure, consider factors that could contribute to potential physical and cognitive issues, conduct a physical examination, order medical testing, and thereafter, develop a differential diagnosis. In 1998, Kenneth Hudnell, Ph.D., published an article that explored the benefits of using visual contrast sensitivity testing as a biomarker for PEAS.

Dr. Shoemaker started using the testing soon thereafter. According to Dr. Shoemaker, the test results indicated that there were distinguishable markers between people exposed to the Pocomoke River and those who were not. At this point, realizing that he was treating patients who were not exposed to pfiesteria, dinoflagellates, or algal blooms, Dr. Shoemaker believed that his patients must have been exposed to water damaged buildings that contained visible mold. In treating the patients who were exposed to water damaged buildings, Dr. Shoemaker would initially remove samples of visible mold from a person’s workplace or residence.

Then he would remove the patient from the exposure and prescribe Cholestyramine. The person would remain on Cholestyramine and away from his or her workplace or residence for approximately two weeks. If the symptoms subsided, Dr. Shoemaker would remove the patient from Cholestyramine and instruct him or her to stay away from the exposure. The patient would then be evaluated approximately two to three ⁵⁷⁵ days later.

Assuming the patient was not exhibiting the previous symptoms, the patient, again, would be exposed to the mold. This exposure would occur without Cholestyramine being prescribed. If the symptoms arose again, the patient would be retreated with Cholestyramine. Not long after, Dr. Shoemaker added blood tests to review whether the treatment was working.

After that, he created a two-tiered case definition. 4 To satisfy the first tier, the following had to occur: (1) a patient had a potential for exposure to water damaged buildings, (2) there was the “presence of multiple health symptoms for multiple health systems,” and (3) confounders were absent (i.e. untreated or uncontrolled medical conditions). If a patient satisfied these requirements, the results from the blood and visual contrast sensitivity tests would be reviewed to determine whether three of the following were present: (1) one of fifty-four kinds of immune response genotypes known as HLA, (2) reduced levels of melancyte stimulating hormone (“MSH”), (3) elevated levels of matrix metalproteinase-9 (“MMP9”), (4) deficits in visual contrast sensitivity, (5) dysregulation of ACTH and cortisol, and (6) dysregulation of ADH and osmolality. According to Dr. Shoemaker, HLA is inspected because it is a genetic measure that reviews immune response genes that “help turn down innate immunity following exposure .... ” When “HLA is working, ... innate immune re-signals get converted into antibodies that then protect [a person].... ” Dr. Shoemaker next explained that the level of MSH is analyzed because it is a hormone that regulates innate immunity in the body. According to him, MSH deficiency is generally present in individuals exposed to water damaged buildings because innate immune responses are not being properly regulated.

Dr. Shoemaker thereafter noted that levels of MMP9 are reviewed because “MMP9 looks directly at a unified presentation of a kind of innate immune element ⁵⁷⁶ called a cytokine----” As for the visual contrast sensitivity test, Dr. Shoemaker explained that this test is used because its results illustrate “inflammatory changes that cause reduction of blood flow in small blood vessels in the retina.” Additionally, Dr. Shoemaker provided that ACTH and cortisol are examined to determine whether there is a “disruption of a secondary mechanism to compensate for original inflammation ...,” and ADH and osmolality are examined to review the hypothalamic center. All in all, these measurements are supposed to illustrate inflammation, which, according to Dr. Shoemaker, is a biomarker for illnesses related to exposure to water damaged buildings. Hung Cheung, M.D. (“Dr. Cheung”), a board certified physician in internal and occupational medicine, testified in opposition to Dr. Shoemaker.

In his “health-based approach” to evaluating patients associated with exposure to mold, Dr. Cheung explained that he reviewed a patient’s complaints and medical history, assessed environmental conditions, and then determined whether environmental conditions were the cause of a patient’s complaints. To evaluate the environment exposure, Dr. Cheung used the four “P’s”: (1) pollution, which could range from the ozone to mold, to endotoxins, (2) pathway, simply meaning the method in which the pollutant travels throughout the building, (3) pressure, which explains the direction of flow of the pollutant, and (4) person, because exposure is not possible without a person. Because there are different types of exposure, Dr. Cheung explained that he had to determine which one caused a patient’s symptoms. Thereafter, recognizing that Dr. Shoemaker could render a diagnosis using the differential diagnosis method, Dr. Cheung testified that the issue of causation has “nothing to do with differential diagnosis.” Instead, he merely believed that Dr. Shoemaker’s differential diagnosis exposed the human health effects being suffered.

Dr. Cheung then explained that the scientific literature does not support the notion that exposure to toxic mold by inhalation in water damaged buildings causes certain human health effects. Ultimately, Dr. Cheung explained that Dr. Shoemaker’s methodology, treatment, and ⁵⁷⁷ opinion regarding causation are controversial and not generally accepted in the scientific community. Approximately fourteen months after the Frye-Reed hearing, 5 the circuit court issued findings of fact. In relevant part, the court made the following findings: Dr. Shoemaker’s Qualifications and Experience 1.

Dr. Ritchie Shoemaker, M.D., is Board Certified in Family Practice. 2. Dr. Shoemaker has no advanced training or certification in toxicology, allergy, epidemiology, genetics, mycology, immunology, rheumatology, industrial hygiene, neuropsychology, pulmonology, endocrinology, or teratology. 3. Dr. Shoemaker employs each of these areas on a regular basis in the practice of medicine. 4. With respect to diagnosis and treatment of human health consequences of persons exposed to toxicity from water damaged buildings, Dr. Shoemaker has been primarily a diagnostician and treating physician.

His approach has been that of a clinician in the practice of medicine. 5. Dr. Shoemaker’s medical group has addressed the medical question of health consequences or illness as a result of exposure in water damaged buildings more than four thousand seven hundred (4700) times since starting this area of interest in his practice of medicine in 1998. 6. In the years following 1998, about seventy-five (75) percent of Dr. Shoemaker’s medical practice was devoted to the diagnosis, care, and treatment of patients who had illness acquired following exposure to water damaged buildings. Now the portion of his practice devoted to this specialized area of medicine is about ⁵⁷⁸ ninety-five (95) percent and has been since 2002, when he sold his family practice and moved into a new medical office and practice. 7.

By 2005, Dr. Shoemaker had treated over three thousand (3000) patients with health problems from exposure to the complex chemical mix found in water damaged buildings. 9. In these cases, samples of visible mold were taken from the home or workplace and sent to a reference laboratory. Also, it was not uncommon to notice odors in areas of water damage. 10. About twenty-five (25) percent of the patients treated by Dr. Shoemaker for illness acquired following exposure to water damaged buildings were referred to him by other physicians.

Dr. Shoemaker’s Use of Differential Diagnosis is with Patients Exposed to Water Damaged Buildings 31. A differential diagnosis is a preliminary or working diagnosis. The follow up treatment and testing is meant to rule in possible, likely causes and rule out other confounders, in order to arrive at a final diagnosis. 32. The use of this method is taught from the first day in medical school.

For centuries, it has been a standard technique utilized by physicians in the diagnosis of illness and in the care and treatment of patients, and it continues to be a standard technique today. 35. [The] method, which [Dr. Shoemaker] followed with each ... [appellee], was to see the patient, take a medical history, perform a physical examination, order medical testing, and then start with a differential diagnosis. 36. In addition to Dr. Shoemaker’s reliance on the history given by the patient and a physical examination, the ⁵⁷⁹ results of certain blood tests and studies were used to show an absence of confounders, such as other diseases that could account for or contribute to inflammatory problems that patients may have. Dr. Shoemaker’s Repetitive Exposure Protocol and Treatment Protocol 37. In order to attempt to establish a causal relationship between the exposure and the health effects or illness, Dr. Shoemaker utilized a repetitive exposure protocol, which is a five (5) step process. 38.

Step one (1) of the protocol is called Base, which stands for baseline. 39. Step two (2) is called AC 1, which means after treatment (Cholestyramine), the first time around. 40. Step three (3) is called HOC, or alternatively, OROC. The acronym HOC stands for patient home off Cholestyramine, if the suspect building is a work place. 41.

Step four (4) is called BOC. The patient is placed back in the building for three (3) days and off the Cholestyramine. If the patient does not become ill, then there is no step five. If the patient does become ill again under BOC, only then does step five (5) occur. 42.

Step five (5), called AC2, means after Cholestyramine, the second time around. 43. Based upon the findings of one hundred and one (101) patients in some forty (40) buildings, Dr. Shoemaker found that there was something in the exposure to the indoor air that was causing the illness. He did not find or conclude that it was exclusively mold itself which was the cause of the illness. 44. The technique of repetitive exposure protocol is an example of a component of differential diagnosis and has been routinely and regularly practiced by clinical ⁵⁸⁰ physicians to prove prospective causation, i.e., prospective acquisition, of illness. 45.

The time honored goal of repetitive exposure analysis is to isolate that exposure, eliminate and rule out confounders, and confirm the cause of illness with diagnostic studies and tests. 46. Under this process, the patient becomes the control for his own health and the short term interventions of three (3) days of exposure and then three (3) days of no exposure is more reliable from a diagnostic standpoint than a longer term period of time or study. 47. The essence of Dr. Shoemaker’s treatment protocol is to eliminate the exposure to potential toxicity on the front end and lower or eliminate toxicity at the back end, through the binding action with Cholestyramine. 48. According to Dr. Shoemaker, Cholestyramine has a positive charge and the toxins have a negative charge, so that they attract one another and bind into a large compound, preventing its reabsorption into the system.

The compound, including the toxins, is eliminated from the system and hence the patient’s toxicity is lowered and their symptoms relieved. 49. The treatment protocol has proved effective in the acute phase illness in thousands of patients who have been treated by Dr. Shoemaker’s group. 50. The results of a treatment protocol also serve as a diagnostic tool. The response to a given therapy or treatment can be an essential element of the ongoing refinement of a differential diagnosis process. 51.

Over a ten (10) year period, Dr. Shoemaker’s treatment protocol underwent eleven (11) refinements or changes, but the basic approach remained the same. 54. Dr. Shoemaker published the treatment protocol as of 2005 in a book called Mold Warriors. ⁵⁸¹ The Two Tier Analysis Employed by Dr. Shoemaker after 2002 55. After 2002, Dr. Shoemaker stopped taking new patients unless they had a chronic fatigue illness. With a larger patient base in this new area of practice, Dr. Shoemaker was able to collect data and to rule out a variety of possible confounders.

He utilized a Two Tier system in arriving at a common case definition of the illness suffered by his new patients. 56. By this time, the water damaged building cohort of Dr. Shoemaker’s practice constituted about two-thirds of his practice. 57. Under the model, the Tier One criteria were to establish that all patients must have the potential for exposure to water damaged building(s) somewhere, and the absence of any untreated and uncontrolled medical conditions that could be a confounder. 58. The second Tier is much more restrictive and precise.

To meet Tier Two of the case definition, a patient must meet at least three (3) of six (6) secondary criteria, to eliminate any false positives in the diagnosis. 59. Dr. Shoemaker is able to reach a diagnosis to a reasonable degree of medical certainty just from taking into account the Tier One factors. Under Tier One, there is (1) a finding of the potential for exposure; (2) the presence of multiple health symptoms; and (3) a ruling out the presence of confounders through the differential diagnosis analysis. This process involves employment of the repetitive exposure protocol.... 60.

By mid-2003, the second Tier criteria were used to increase restrictiveness so that no false positives would be included in the diagnosis. The second Tier findings provided increased weight to the opinion, but was not necessary in order for Dr. Shoemaker to diagnose biotoxin or toxin illness from exposure to water damaged buildings to a reasonable degree of medical certainty. ⁵⁸² 61. The degree of certitude solely based on Tier One analysis is over fifty (50) percent. Dr. Shoemaker would not proceed with the Tier Two analysis if the patient does not pass the Tier One level.

The degree of certitude increases to the high nineties (90) if the diagnosis is based on both Tiers. 62. The blood tests and studies in the Tier Two inquiry are attempting, first and foremost, to measure inflammation and, in the process of doing so, assist Dr. Shoemaker in isolating the potential cause of illness from other confounders. 63. There are six (6) secondary criteria in the Tier Two analysis. They are: 1) The presence of one of fifty-four (54) kinds of immune response gynotypes, call HLA, a genetic marker found on chromosome 6[;] 2) A reduction of an inflammation preventing hormone, Melanocyte Stimulating Hormone, or MSH; 3) An elevated level of an inflammation representing enzyme called Matrix Metallic Proteinase Nine or MMP9; 4) An abnormal relationship of hormone pairs ACTH, a hormone that stimulates adrenals to cortisol; 5) An abnormal relationship of hormone pairs Antidiuretic hormone ADH to osmolality; and 6) A visual contrast test. 64.

Criterion two (2) under the Tier Two analysis, the reduction of MSH, is found in over nine-two (92) percent of Dr. Shoemaker’s patients. This MSH hormone is important in the regulation of innate immune responses and therefore the deficiency results in abnormalities of the innate immune responses. 65. The third criterion, elevated MMP9, is quite common in the biotoxin and toxin illnesses treated by Dr. Shoemaker. The list of illnesses for which MMP9 is elevated is quite small.

An elevated level of MMP9 is an example of inflamation, which can also be found in a ⁵⁸³ patient with acute lung disease, connective tissue problems, or multiple sclerosis. 66. Criterion number four (4), abnormal relationship of ACTH to cortisol, is something that Dr. Shoemaker has encountered in over four thousand (4000) patients. 67. The blood work and visual contrast, which is criterion six (6) in Tier Two are part of the later stages of the diagnostic protocol used by Dr. Shoemaker, but are not part of the treatment protocol. 68. Dr. Shoemaker’s data base showed that where there were at least three (3) of the six (6) criteria found, all of those patients were in the exposed category and had already been diagnosed under the Tier One analysis as ill from exposure to a water damaged building. 69.

The data base showed that where there were only one (1) or two (2) but less than three (3) of the criteria, all of those persons were in the control group, i.e., those who had not been exposed to a water damaged building. 70. The test for the presence or absence of these six (6) criteria were all standard blood tests that were performed by a commercial laboratory. The results were placed in the patient’s medical file and became part of the data base that Dr. Shoemaker maintained for all of his new patients with exposure to water damaged buildings. 71. Dr. Shoemaker’s patients who are diagnosed with a biotoxin or toxin illness have an innate immunity response and not acquired immunity, such as someone suffering allergy or asthma. 72.

In the early years, up until 2003, the blood test results that were ordered were essentially normal. Then, starting in mid-2003, Dr. Shoemaker ordered the Tier Two blood studies and tests that looked at the markers for innate immune response activity. He found that results were now abnormal in many respects. ⁵⁸⁴ 73. Under this newer approach the focus was on innate immunity and inflammation was consistently identified as the central and major problem.

Dr. Cheung’s Methodology 143. Dr. Cheung is conducting two epidemiology studies. One is in Maryland and involves seven thousand six hundred (7,600) participants. The study involves over three hundred (300) sites and there are air samplings for mold, surface swabs for mold in the air handling units, measurements for endotoxins, skin cells, and measurements for sixty-four (64) different compounds that are within indoor environments. 144.

To assess whether the exposure to the chemical mix in the work environment is causing illness to the occupants, Dr. Cheung relies upon the concept of four (4) “Ps”. 145. The first “P” is the pollutant, which could be anything: maybe the ozone, or the mold, or the endotoxin, or the odor, or various other things. 146. The second “P” is the pathway which is how the pollutant travels and how it gets around in the exposed location or building. The ventilation system is often a major factor under the second “P”. 147.

The third “P” is pressure, which explains the direction or flow of the pollutants along the pathway. 148. The fourth “P” is the person. Without any person, for example, in a warehouse, there is no exposure to any human and hence there are no health problems. 149. The goal of building remediation is to eliminate at least one of the first three (3) “Ps” so that persons who have to work or live in water damaged buildings are no longer exposed. 150.

In looking at the issues of association or causation in exposure to the combination of chemicals in water damaged buildings, the strength or potency and quan ⁵⁸⁵ tity of various chemicals is important in determining whether there [may be] a much higher synergistic affect [sic] based upon the particular mix. 151. In determining causation of adverse health effects from exposure to toxic mold in water damaged buildings, it is important that a diagnostician consider the synergistic effect from the combination of chemicals in any given building, and not simply consider strength or potency and quantity of toxic mold alone. 152. Most mold assessment exposures are subjective by their very nature. Even if scientific methods are used, an objective mold assessment is very difficult to obtain and rarely used without the subjective complaints.

Testing techniques and methods are static by their nature. Exposures are ever-changing and therefore a static test cannot be an accurate measure. Each of the four (4) “Ps” is constantly changing. Dr. Cheung’s Scientific Opinion on Causation in These Proceedings 155.

Dr. Cheung has testified that, in his opinion, the use of differential diagnosis procedure and diagnosis of CBAI fails to establish general causation or specific causation and is therefore unreliable. It merely gets to what the health condition may be, but without the causation analysis, it fails to prove causation. 156. General causation in environmental medicine and research, in Dr. Cheung’s opinion, is the equivalent of scientific causation which is at the nine-five (95) percent level of probability. It must be proved to this degree of certainty, by a rigid research based standard, according to Dr. Cheung. 157.

In Dr. Cheung’s opinion, causation analysis and scientific or general causation really have nothing to do ⁵⁸⁶ with differential diagnosis, the method followed by Dr. Shoemaker. 159. Dr. Cheung rendered his opinion that Dr. Shoemaker’s diagnosis of CBAI is not generally accepted ... 160. Dr. Cheung testified that, in his expertise, water damage in buildings may be the cause of health consequences and human health illness. He breaks the human health consequences into three categories: First, is the allergic or hypersensitivity group.

Second, it is classified as infection or infections. The third category is the toxic effects associated with mold. The toxic effects, in Dr. Cheung’s opinion, are usually associated with ingestion and not inhalation. 162. Dr. Cheung contends that the various studies do not support Dr. Shoemaker’s conclusions.

These studies do not show that exposure to toxic mold by inhalation in water damaged buildings are in high enough concentrations to show an association with fatigue, memory loss, join[t] pain, muscle aches, confusion, weakness, depression, or disorientation. 163. Dr. Cheung acknowledged that if forty (40) people are in a water damaged building where visible mold is present and can be smelled, that it would be a good indication of an exposure. 164. Dr. Cheung noted that the Maryland State Task force on Indoor Air Quality Trial Report of July 1, 2002, investigated a wide variety of biological agents present in indoor environments that could potentially cause health problems. 165. The report specifically stated that molds and fungi can cause significant human health effects, including allergies, hypersensitivity pneumonitis and other health effects. ⁵⁸⁷ 166.

The specific health effects depend both on the nature and extent of the exposure and the underlying health status of the exposed individuals. Mold growth in buildings can have adverse health consequences. 167. The Report concluded on page eleven (11) that there is an inadequate base of scientific knowledge to get health-based mold standards for buildings because of uncertainties about the levels of mold, the relationships between mold exposure and different health effects, and differences in susceptibility from person to person. 168. Finally, the Report stated that exposures to indoor mold contamination can and should be minimized, and mold growth and contamination in offices can and should be prevented. 169.

Dr. Cheung’s opinion is that Dr. Shoemaker’s diagnosis, treatment methodology and opinion on the [causal] relationship between human health effects and water damaged buildings is not generally accepted by the scientific community. 170. Dr. Cheung does not have any problem with Dr. Shoemaker’s use of Cholestyramine to treat patients for exposure to mycotoxins in water damaged buildings nor to his treatment regimen or ordering them to be removed from the workplace. 171. Although he has no criticism of these steps by Dr. Shoemaker in his treatment, he does not believe that Dr. Shoemaker’s treatment protocol proves either general or specific causation. 172. Dr. Cheung’s complaint is that Dr. Shoemaker does not have the field investigators investigate the building to determine scientifically what chemicals or toxins are actually present in the indoor air and, if any, whether they are of sufficient potency to cause, generally and specifically, adverse health consequences to any of the buildings occupants. ⁵⁸⁸ 173.

Dr. Cheung believes the physician should guide the investigation as well as the communication and resolution of the problem. He actually goes out to the building site himself and actually crawls around and does sampling himself, so that he knows what the persons are exposed to, at least at the time that he is there .... 174. Dr. Shoemaker testified that this hands-on sampling is not part of his job as a diagnosing physician. Dr. Cheung does not know whether Dr. Shoemaker actually does this hands-on investigation sampling himself or relies upon others.

An opinion was issued approximately six months after the findings of fact. In concluding that Dr. Shoemaker’s differential diagnosis method was reliable and acceptable to establish general and specific causation, the circuit court indicated that the “question of admissibility of expert medical testimony to prove general or specific causation appears to be a case of first impression in Maryland.” Indeed, noting that there was “no judicial consensus regarding admissibility,” the court explained that there were two “distinct” approaches in toxic tort cases: (1) the toxicological approach 6 and (2) the clinical-medical approach. 7 The circuit court explained that the toxicological approach recognizes that the differential diagnosis method was reliable. ⁵⁸⁹ However, the court noted that a differential diagnosis alone was not sufficient to establish general or specific causation under the toxicological approach. Because of that, the circuit court explained that the toxicological approach “deemphasizes the temporal relationship between exposure to a toxin and the onset of symptoms, focusing on specific dose-response relationships for the toxins.” Conversely, the court noted that the clinical-medical approach “acknowledges that differential diagnosis is the ... generally accepted method by which a clinician diagnoses the various illnesses he or she encounters in a myriad of patients.” Moreover, the circuit court explained that the clinical-medical approach permits “a clinical physician to express an opinion, derived from differential diagnosis, that a particular toxic substance caused the patient’s symptoms.” Inferring that the toxicological approach was undesirable because it was “inflexible,” the circuit court articulated: Even if scientific methods are used, an objective and accurate mold assessment is very difficult to obtain, and is rarely used without subjective complaints. Testing techniques and methods are static by their very nature.

Exposures, on the other hand, are ever changing and therefore a static test or even a series of such tests cannot be an accurate measure of the levels of concentration of toxicity or the duration of an exposure in any particular area of a water damaged building. Nor do static tests truly reflect a person’s exposure over an extended period of time. No government agency has yet established a standard to determine a safe range or a dangerous range of indoor mold or other mycotoxin levels. Strict adherence to the toxicological approach would thus require a plaintiff to present information that does not yet exist.

Without such information, there is no redress for the serious health problems that he or she may have suffered. One can only hope that future plaintiffs may find their luck enhanced by further scientific research. Today’s plaintiff, under the toxicological approach, must accept that mold cannot be the scientific or legal cause of his or her symptoms, despite general acknowledgment that molds and fungi can cause significant human ⁵⁹⁰ effects and the standard practice of vacating and remediating water damaged buildings where molds and other toxins are present. Noting that the clinical-medical approach would be used to determine the admissibility of Dr. Shoemaker’s testimony, the court opined: An integral part of any differential diagnosis process is a determination by the clinician of the general and specific causation of the patient’s illness.

This Court finds that an expert medical opinion based upon a properly conducted differential diagnosis is reliable. Therefore, a medical opinion based upon this methodology is admissible to prove general and specific causation of illness from exposure to toxicity in a water damaged building. After that, the circuit court concluded that Dr. Shoemaker’s testimony was admissible because: (1) The medical community is the relevant scientific community to determine whether differential diagnosis is a well recognized and generally accepted procedure. (2) Differential diagnosis is well recognized and generally accepted in the medical community.

(3) Two of the well recognized methods to establish the presence of toxicity and an exposure are the presence of black or visible mold and an odor. Dr. Shoemaker verified the presence of visible mold and an odor in the building where [appellees] and other employees were exposed. (4) There is no requirement that toxic mold alone be identified or determined to be in sufficient quantity to be the pollutant. In establishing an exposure, the medical doctor must consider the combination or chemical mix present in any particular water damaged building for a finding of general and specific causation.

(5) Dr. Shoemaker was aware of the exposure to microbial growth and proliferation before meeting with [appellees]. He ... met with [appellees] for purposes of diagnosis and treatment rather than litigation. Dr. Shoemaker’s expertise ⁵⁹¹ in treating patients exposed to toxicity dates back to 1980, and is not litigation-driven. (6) Dr. Shoemaker took a detailed medical history and conducted a physical examination of [appellees] as a part of his routine diagnostic process.

(7) Dr. Shoemaker determined that there was a cohort of fifty (50) employees who were exposed. Of that number, eleven (11) employees were determined not to be ill and therefore were not tested. Dr. Shoemaker found twenty-two (22) employees who showed evidence of illness that could be ascribed to the exposure. Seventeen (17) other employees were examined and tested by other health care providers.

Where a number of people become ill following an exposure, the temporal relationship between the exposure and illnesses becomes stronger and furnishes compelling evidence of causation. (8) Dr. Shoemaker relied upon strong evidence of the temporal relationship between the onset and exacerbation of symptoms upon treatment and removal from exposure. He also relied upon the reported relapse of symptoms in three (3) of [appellees] following their exposure to boxed files that had been removed from the vacated office building. (9) Dr. Shoemaker, after performing a differential diagnosis, was able to reach a final diagnosis to a reasonable degree of medical certainty as to [appellees].

In doing [so], he relied upon evidence of an exposure, the presence of multiple health symptoms, and diagnostic studies and blood tests, to rule in probable causes and rule out alternative causes of [appellees’] illnesses. The Tier Two (2) studies confirmed the final diagnosis. Because appellant noted a timely appeal, we must determine whether the circuit court was correct in its Frye-Reed determination. DISCUSSION The present case was remanded to determine whether the “methodologies used for diagnosis and theories regarding the ⁵⁹² causal connection between mold exposure and certain human health effects are generally accepted in the scientific community.” Chesson, 399 Md. at 336 , 923 A.2d 939 .

After the Frye-Reed hearing, the circuit court concluded that the differential diagnosis performed by Dr. Shoemaker was reliable and acceptable to establish general and specific causation. On appeal, we must conduct a de novo review and independently determine whether Dr. Shoemaker’s methodologies and theories are admissible under the Frye-Reed standard. See