Unexplained deaths due to possibly infectious causes/ICD 799: Does autopsy provide the answer?

Occasionally a patient presents with a serious, acute, progressive illness which defies diagnosis. Some of these patients recover without a diagnosis, but some die, after extensive non-diagnostic evaluation. Death is attributed to a nosocomial complication, to the unidentified process, or to both. The CDC has developed a community-based surveillance system to report unexplained deaths due to possibly infectious causes (UDPIC) in order to detect emerging infectious diseases. A related ICD-9 code is 799: "ill-defined and unknown causes of morbidity and mortality." I established a case definition for UDPIC/ICD 799 which includes evidence of systemic involvement on admission, absence of preexisting serious illness, survival in the hospital for at least 72 hours before death, consultation to multiple medical subspecialty services (to include at least infectious diseases or rheumatology) and no diagnosis at death. In order to see if postmortem examination provided an answer to the etiology of these illnesses, I retrospectively reviewed all autopsies done from 1986 to 1995 to identify patients who might fit these criteria. A total of 2314 autopsies were reviewed; the clinical summaries from 18 patients were compatible with UDPIC/ICD 799. Review of available 15 medical records disclosed a total of 3 who in fact fit the case definition. The final diagnosis provided by autopsy was autoimmune disease in two (Wegener's and interstitial pneumonitis) and infectious disease in one (influenza A). A better understanding of the distribution of final diagnoses (if any) in patients with UDPIC/ICD 799 would help guide diagnostic approaches and therapy. We now freeze tissue at autopsy for patients who die without a diagnosis for future evaluation using new techniques or diagnoses.