Cost-effective diagnostic test sequencing.

Proper diagnostic test selection and logical sequencing can minimize cost without compromising care. This study analyzes the logic for sequencing tests either in series (one after another) or in parallel (simultaneously). A model is created using 2 diagnostic tests for 2 diseases. Tests are assumed to have perfect performance characteristics. Factors involved in cost-effective test sequencing include cost of each test, test performance characteristics, per diem hospital charge, and the clinician's prior probability of the suspected diagnosis based on history, physical examination, and previous laboratory data. At a given point of clinical suspicion, cost-effective sequencing strategy should shift. In general, a cheap test can effectively be used in parallel even at low diagnostic probabilities; an expensive test should, in general, be used in series only when there is a high prior probability of diagnosis. High per diem hospitalization costs--such as for a patient in the intensive care unit--favor in parallel testing. Clinical acumen and suspicion of diagnosis (prior probability) primarily direct cost-effective diagnostic test sequencing. Decision analysis of diagnostic test sequencing represents a technique for making cost-effective decisions for sequencing and, thereby, minimizing costs while achieving optimal patient care.