Common diagnostic test panels for clinical evaluation of new primary care outpatients in Japan: a cost-effectiveness evaluation.

BACKGROUND The Japan Society of Clinical Pathology (JSCP) has developed a guideline for common diagnostic test utilization in new primary care outpatients. To determine the scientific and economic validity of the JSCP panel testing system, we analyzed cost-effectiveness parameters of test panels advocated. METHODS The "Essential Laboratory Tests" panel (2) [ELT(2) panel], a package of common diagnostic tests added to the ELT(1) baseline health-status screening panel, was applied to 540 new outpatients who visited the Comprehensive Medicine Clinics in an academic medical center during 1991 to 1997. A "useful result" (UR) of testing was defined as a finding that contributed to a change in a physician's diagnosis- or decision-making, relating to a "tentative initial diagnosis" (TID) obtained from history and physical examination alone. RESULTS Clinical usefulness was demonstrated in 259 patients with ELT(2), in whom 398 URs were generated. Clinical effectiveness (UR/TID) ranged from 1.65 (hematological) to 0.088 (neurological disease), with a cost disparity from yen1251 ( approximately $10) to yen23 037 ( approximately $200) per UR. A total of 1137 tests generated URs. We further assessed the clinical effectiveness and economic efficiency (cost/UR) of ELT(1) and restructured panels. Use of the ELT(1) alone generated 244 URs in 167 patients. The poor efficiency of the ELT(1) panel was markedly improved with the addition of certain ELT(2)-specific tests in liver/pancreatobiliary, metabolic/endocrine, and cardiovascular disease groups. CONCLUSIONS A wide disparity in the utility of ELT panels in different patient groups does not support the JSCP recommendation of their routine use for new outpatients. Selective test combinations should be used in selected patient groups.