Laboratory screening method for selection of healthy volunteers.

The aim of laboratory screening in Phase I is to exclude subjects with subclinical illness, who might be at increased risk in the study, and who might also adversely influence interpretation of the results. A new method for laboratory screening, based on Bayesian probability theory, is proposed, which consists of: 1. Drawing up a list of diseases to be excluded. 2. Defining for each disease, the maximum acceptable risk that an included subject could be affected by it. 3. Identifying one test for each disease. 4. Using a contingency table to calculate the specificity of the test and integrating the estimated prevalence of the disease from epidemiological data. 5. Applying the percentage obtained by the calculation of specificity to the previously determined distribution of values in the volunteer population to identify the threshold value for inclusion. Use of this deductive method in screening volunteers for Phase I trials affords increased security of selection, while reducing the number of non-pertinent exclusions because of laboratory findings.