Opportunistic discovery of occult disease by use of test panels in new, symptomatic primary care outpatients: yield and cost of case finding.

BACKGROUND Diagnostic test panels have been advocated by the Japan Society of Clinical Pathology for evaluation of presenting complaints of new outpatients in primary care medicine. The tests have additional potential utility for opportunistic finding of asymptomatic diseases, but data are lacking on the number of new conditions identified by the test panels and on the cost per identified case. METHODS We studied 540 new, symptomatic patients at the Comprehensive Medicine Clinics of National Defense Medical College during 1991-1997. All underwent testing with the "Essential Laboratory Tests" panel (2) [ELT(2) panel]. This panel includes hematologic tests, urinalysis, total protein, C-reactive protein, albumin, cholesterol, triglycerides, glucose, urea nitrogen, creatinine, uric acid, serum protein fractionation, six enzymes, and optional tests, including x-rays, electrocardiogram, and fecal occult blood. RESULTS The ELT(2) panel uncovered 276 additional diagnoses of asymptomatic disease or abnormal health status. The most frequent occult condition was hyperlipidemia (100 cases) followed by liver dysfunction (53 cases). Clinical efficiency of the panel (occult diseases/patient) varied depending on the category of tentative initial diagnosis, with the highest efficiency in patients with cardiovascular disease. We created smaller panels by combining 11 basic tests [called the ELT(1) baseline panel] with one or more additional tests from the ELT(2) and analyzed their cost-effectiveness. Addition of four tests (total cholesterol, alanine aminotransferase, glucose, and uric acid) improved both clinical efficiency (0.41 occult disease/patient) and economic efficiency [ 2372 yen (approximately $22.50 US)/occult disease] at a cost-effectiveness of 177 yen per incremental case of occult disease. Addition of further tests decreased cost-effectiveness. CONCLUSIONS Although the ELT(2) panel has supplemental utility for opportunistic screening of some significant, occult diseases and conditions, universal utilization of the full panel is not supported by the cost-effectiveness found in this study.