ESTABLISHING REFERENCE INTERVALS FOR DPCS FREE TESTOSTERONE RADIOIMMUNOASSAY

Objective: To establish reference intervals for serum free testosteron e for DPC's Free Testosterone assay. Methods: We used data from health y subjects and patients to determine reference intervals by parametric and non-parametric methods after partitioning by sex and age. Results : In males, there was a significant decrease in free testosterone conc entrations with age. Reference intervals derived from a combination of 2075 ''healthy'' and patients' results gave similar values by paramet ric and nonparametric methods. However, the subgroups failed the test for Gaussian distribution. For each decade from 20 years on and greate r than or equal to 60 years, the intervals based on 2.5th and 97.5th p ercentiles were: 24.1-94.8, 25.0-89.3, 23.4-81.7, 22.5-80.4, and 21.5- 74.3 pmol/L respectively. In females, there was little change with age . The frequency distribution of 1915 patients was positively skewed, a nd showed a wider range than ''healthy.'' Using square roots of values gave a Gaussian distribution. The central 95% intervals based on 187 ''healthy'' subjects were: 0.5-8.1 and 0.0-6.4 pmol/L for 20-59 and gr eater than or equal to 60 years, respectively. Conclusion: Developing reference intervals for free testosterone was complicated by the need to partition data by gender and age, difficulty in establishing diseas e in subjects and presence of physiological and other factors which ca n affect concentration in health and disease.