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CLINICAL TOXICOLOGY, 15(1), pp. 1-11 (1979) The Practice of Medical Toxicology* ERIC a CQUSTOCK,t M.D., A.B.M.T. Department of Medicine Baylor College of Medicine Houston, Teas 77030 Department of Pharmacology University of Teas Medical School at Houston Houston, Teas 77030 ABSTRACT Two hundred twelve consecutive cases presenting to a medical toxicologist related to chronic occupational exposure (49%), acute occupational exposure (24%), and nonoccupationai ex posure (27%). Chief complaints were respiratory (36%), be havioral (28%), neuropathy (17%), and organic brain syndrome (10%). in 90% of patients, litigation was in process or under consideration. Referrals were from plaintiff attorneys (37%), from employers, insurance companies, and defense attorneys (20%), and from physicians (24%). Outcome of assessment revealed 55% to be unrelated to toxic substances, 39% probably related, and 6% positively related. *Presented at the 1978 Annual Meeting of the AACT, Chicago. tAddress reprint request to 1802, Medical Towers, Houston 7703a 1 ucc 057809 2 COMSTOCK INTRODUCTION Medical toxicology is a new medical specialty with certification of physicians first offered in 1975. Twenty-six of the 30 physicians certi fied from 1975 through 1977 reside in the United States [1]. In the ab sence of a residency in medical toxicology, most of the diplomates have primary training in other specialty arear such as pediatrics, emergency medicine, or clinical pharmacology, wh.ch they continue to practice pri vately or as faculty or staff in universities or industry. The qualifica tions for the boards specify that after 1984 candidates must have com pleted an approved 2-year residency in medical toxicology. The only residency now existing in the world was nitiated in 1976 in Montevideo, Uruguay [2], Several centers in the Uni ed States have active interest in developing a residency but no prograj i is likely to be initiated prior to 198a The professional and economic feasibility of medical toxicology as a single specialty has not yet been demonstrated. It is assumed that increased interest in the impact of toxic substances on human health will generate positions in industry, governmental agencies, and univer sities for graduates of a medical toxicology residency. Only a few in dividuals in the United States have accumulated experience with a pri vate practice limited completely to medical toxicology. The opening of an office for the practice of medical toxicology in a professional building near the Tegas Medical Center was proceeded by 14 years of full time involvement in clinical toxicology based in labor atory, academic, and clinical research and service institutions. Con sultation on diagnosis and treatment of human illness thought to be re lated to toxic substances was provided as requested. As a part-time private practitioner, 1300 eases were attended of which approximately 900 were admissions to intensive care units for acute poisoning. Pa tient attendance varied from 1 to 96 hours. During the peak hospitalbased practice in 1967, seven patients were attended concurrently as admitting physician in five intensive care units. With the emergence of the full-time emergency physician and the hospital-based intensive care physician, the need for the toxicologist as a primary care practi tioner has decreased and the practice was limited to consultation only. METHODS A retrospective analysis was conducted on the records of 212 con secutive cases presenting in private office for the practice of medi cal toxicology. Except for consultations requested on patients already In the hospi tal, all procedures were performed on an outpatient basis. Patients from out of town generally stayed at a nearby hotel for the 1 to 3 days ucc 057810 THE PRACTICE OF MEDICAL TOXICOLOGY 3 required for clinical evaluation. Toxicologist-patient contact averaged about 3 hours and included the usual medical evaluation Including com plete physical and neurological examination. Most patients were in addition administered a brief neuropsychological test battery and an MMPL Special attention was given to occupational history starting with the last year in school. All jobs held and all potent!?' occupa tional exposure to toxic substances were explored. Inqi iry was made into food habits, drug use, hobbles, and avocations. Employers were sometimes contacted to further clarify the nature of toxic hazards, al though frequently this was not helpful. When required, additional diag nostic procedures, such as laboratory examinations, EMr, EKG, pul monary functions, and complete Halsted-Reitan neuropsy biological batteries, were obtained during subsequent days. Copies of the hospi tal records and reports from previous physicians were oviewed. In quiry was made concerning other individuals who sustained the same or similar exposure. Epidemiologic investigation frequently provides Increased certainty to the determination of the etiOlogic relationship. Occupational health and industrial hygiene monitoring records were obtained, if possible. Assessment of causal relationship frequently required literature searches using Medline and Toxline data base and manual search of tbs toxicology library- Recovery of appropriate original publications varied from 1 or 2 to more than 50 reprints. A final decision on eti ology sometimes required 3 to 4 weeks depending upon literature availability. Baaed upon the above data and the clinical experience of the author, the etiologlc role of toxic substances was assigned to one of three categories: none, probable, or positive. Cases where exposure was dearly insufficient, where the clinical syndrome Is one not associated with the substances involved, where clinical manifestations did not occur in an appropriate time frame, or where other disease processes dearly provided a more tenable hypothesis were assigned to "none." Where the clinical syndrome was one reasonably associated with the alleged substance, where the time frame was appropriate, where suf ficient dose appeared probable or when multiple cases occurred from the same environment, and where no more reasonable medical cause could be determined, the cases were assigned to "probable." Although a causation was not proven beyond any doubt. It was more likely than not, permitting these cases to meet the test of reasonable medical probability. Cases were assigned to "positive" when in addition to the, conditions for probable, objective evidence supported overwhelming exposure, environmental monitoring established the presence of the toxic substance in hazardous quantities, characteristic biochemical changes occurred in the patient and/or the substance, or its deriva tives were identified in biological specimens in quantities consistent with potential!; hazardous exposure. Some cases clearly meeting the i ucc 057811 4 COMSTOCK . (ar Positive" concerning a brief acute intoxication were ftmvnrrnded to 'probable" or "none" when the chief complaint was mnMn^MT long-term disability with questionable or no relationship tothe initial acute episode. RESULTS Referral sources for 212 consecutive cases presenting to a private medical toxicology office are displayed in Table 1. Referral from plaintiff attorney offices accounted for more than one-third. Such cases often are not yet Involved in any legal action but are referred for advice to the patient and the attorney concerning probability of causal relationship. Physician referrals amounted to one-fourth of the cases. Referrals from Insurance companies provided 11.7% 10.4% were referred by defense attorneys and legal action of some type always was in process. Other patients and self-referral ac counted for 8%. All other sources provided 8.4%. Source of alleged exposure is presented in Table 2. 73.1% origin ated from the work place, and 10.4% were nonoccupational acute ex posures of which about half were acute hospital care patients. Mis cellaneous circumstances accounted for approximately 13%. "Unknown" Included patients who believed themselves to be poisoned but could not account for route or occasion when poisoning might have occurred. The nature of clinical complaints is presented in Table 3. Multiple systems frequently were involved, but only major complaints are listed. TABLE L Distribution of 212 Consecutive Cases by Referral Source Source n% Attorney-plaintiff 78 36.7 Physician 52 24.0 Insurance company 25 1L7 Attorney--defense 22 10.4 Patient 17 8.0 Employer 9 4.2 Union 5 2.3 Service organization 3 L4 Industrial Accident Board 1 0.4 * ucc 057812 THE PRACTICE OF MEDICAL TOXICOLOGY 5 TABLE 2. Distribution ol 212 Consecutive Cases by Type of Exposure Type n% Occupational chronic Occupational acute Nonoceupational acute Drug abuse Adverse drug effect Unknown Monoccupationai chronic Self-inflicted Other 104 49.4 so 23.7 22 10.4 9 4.2 7 3.3 7 3.3 6 2.8 S 2.3 2 as TABLE 3. Presenting Problems in 212 Consecutive Cases* Organ system n% Respiratory Behavioral Neuropathy Organic brain syndrome Skin Death Cardiovascular Hematopoietic Other Cancer Hepatic Coma Trauma Renal 76 36.0 80 28.0 36 17.1 21 9.9 17 8.0 15 7.1 9 4.2 8 3.8 8 3.8 6 2.8 6 2.8 5 2.3 2 1.0 1 as "Multiple system involvement occurs. ucc 057813 6 COMSTOCK TABLE 4. Geographic Distribution of 212 Consecutive Cases n% Greater Houston Other Texas cities 15 Tyler 9 Beaumont 15 ` .Dallas-Fort Worth 13 Austin 2 Galveston 3 El Paso 1 Victoria 1 134 59 63 * 27 Other states Wyoming Alaska Nevada Pennsylvania Louisiana Tiwtiflnfl Arkansas Florida Ohio Utah Massachusetts Total 1 3 1 1 5 1 2 1 1 1 1 * 19 9 212 Some patients had minor complaints Involving almost every organ sys tem. Hie respiratory system was most frequently Involved. Behavioral problems excluding organic brain syndrome were very common, with anxiety neurosis with or without depression the most common. Neuro pathies were the third most frequent presentation. Among 212 cases, in 15 the issue was the cause of death. Geographic distribution is shown In Table 4: 63% originated In the ucc 057814 THE PRACTICE OP MEDICAL TOXICOLOGY 7 TABLE 5. Assessment Outcome by Referral Source for 121 Consecutive Cases Percentage distribution Referral source Number None1 Probable^ Positive*1 Attorney--plaintiff Physician Insurance company Attorney--defense. Patient (sell) Employer Union Service organization Industrial Accident Board Total cases: 42 28 15 14 9 7 3 2 1 121 45 47 87 25 40 53 64 28 67 33 71 28 33 67 50 50 100 0 55 39 7 7 6 7 0 0 0 0 0 6 *Nooe: No toxicologic basis. bprobahle: Toxicologic basis confirmed clinically Le., reasonable medical probability. cPositive: Toxicologic basis established beyond any reasonable doubt greater Houston area, 27% were referred from other Texas cities, and 8% were from out of state. Assessment outcome is presented in Table 5 for 121 consecutive cases. Etiology was determined to be toxic substances in 45% and un related to toxic substances in 55%. The relationship could be considered 'positive" in only 6% of the cases. Table 6 displays an inventory of substances alleged to have caused poisoning. This illustrates the diversity of substances which come under consideration. As indicated in Table 5, the etlologlc role could not be supported in 55% of the cases. DISCUSSION The private practice of medical toxicology Involves an adult popula tion almost exclusively. Association of die illness with employment is UCC 057815 TABLE 6. Inventory of Substances Alleged as Causes of Poisoning Substance Pharmaceuticals Number Subtotal 15 % 7 Substance Alcohol Number Metals 38 18 Inorganics Aluminum alkyl 2 Ammonia 3 Antimony 1 Asbestos 2 Arsenic 8 . Carbon monoxide 2 Chromium 1 Chlorine 2 Lead 15 Oust, inorganic 3 Manganese 1 Fluoride 3 Mercury 5 Hydrogen sulfide 1 Molybdenum 1 Hydrochloric acid 2 Nickel 2 Nitrogen dioxide 1 Titanium 1 Silica 2 . Vanadium 1 Sulfur dioxide 2 Pesticides 22 10 Allphatics Chlordane 2 Acetone. 1 DDVP 1 Carbon tetrachloride 1 Diazinon 2 Chloramine 1 Dursban 1 Ethyl acrylate 1 Subtotal % 3 1.5 23 11 33 16 COMSTOCK THE PRACTICE OF MEDICAL TOXICOLOGY Dlsyston Leptophos Malathlon Naled Paxathion Propanil Zinc phosphide Aromatics Aniline Benzene Blsphenol D1chlorobenzene Dinitrochlorobenzene # Polychlorinated biphenyl Pyridine Toluene Toluene dllso- cyanate l 7 2 1 .2 1 2 1 1 3 1 1 1 3 4 5 Formaldehyde Hydrazine Phosgene Methyl bromide Methyl ethyl ketone Methylene chloride n-Heane Perehloroethylene 1,1-Trichloro- ethaae Styrene Vinyl chloride Others Cyelonite Cyclohemne Organic vapors ' Unknown substances 1 1 1 1 2 1 8 2 3 2 7 2 1 3 19 36 ucc 057816 1.5 9 17 10 COMSTOCK alleged in 75% of the cases. Nonoccupattonal personal Injury is al leged in about 15% of the eases. Some type of litigation has been ini tiated or is being considered in 90% of the cases. The major issue to be resolved is causation, while consultation on treatment is less fre quently required. Exposure to toxic substances had terminated weeks to years prior to examination in it jst cases. Because exposure usu ally was remote in time, unequivocable proof of association .with toxic substances was rarely possible. Because the outcome of litigation is Influenced frequently by the toxicology consultation, the results are almost always scrutinized closely by all parties in the adverse ry system. Rendering an opinion after a brief office consultation is rarely satisfactory. The spectrum of substances involved in a routine office practice is so broad that most cases become miniature die.cal and literature research pro jects before an opinion can be developed. The time invested in each case differs significantly from the usual medical practice, ranging from an hour to as much as 30 hours. The frequency of involvement of the medical toxicologist with med ical legal problems is a reflection of our chemosynthetlc environment. Since the overwhelming majority of toxic substances are products of human manufacture, routes for economic recovery for injuries through the judicial system are potentially open. Bespits the apparent high liability lor requirement of sworn testimony, depositions or court ap pearances occurred on the average of two times per month. As is common with malpractice cases, potentially toxic exposures become the subject of litigation as the result of comments made by physicians which are inappropriate or misunderstood by the patient. Association of an illness with employment is sometimes made rather Indiscriminately without an understanding of the relationship. Many of tbs 55% of cases dassified as unrelated were precipitated by com ments such as "those chemicals have eaten away half your lung," "I would never work out there with ail those poisons," "everyone knows these chemicals cause cancer," or "let me have your spinal cord be cause I'm doing research on whether lead causes your disease." The physician1 s role in provoking morbidity unrelated to toxic substances has been discussed [3], In contrast, the work-related neuropathies are commonly misdiag nosed as amyotrophic lateral sclerosis or multiple sclerosis. The nature of a patient1 s occupational exposure to toxic substances often is not explored as a routine part of the clinical evaluation. Experience with the private practice of medical toxicology affirms the continuing need to encourage more emphasis on clinical toxicology in the medical curriculum. More general recognition of medical toxi cology Is needed to permit consultation early in the dinical course of an lilnees. ucc 057817 THE PRACTICE OF MEDICAL TOXICOLOGY REFERENCES 11 [1] H. Redetxkl and J. E. Ott, Functions and goals of the American Board of Medical Toxicology of the Amerira Academy of Clini cal Toxicology, J. AnaL ToxicoL, 2, 153-1'>4 (1978), [2] E. G. Comstock, G. Fernandez, A. C. Esponda, H. Decedo, and J. Pronczuk de Garblno, Toxicology and clinical toxicology in Uruguay, Submitted to Clinical Toxicology. [3] E. G. Comstock, Morbidity due to non-poiso> ing, J.' Occup. Med., 20, 755-758 (1978). UCC 057818