Comparison of free @entity251 results by analog radioimmunoassay and calculated free XXXX in an ambulatory clinical population.

@entity1 @entity251 @entity6632 @entity443
INTRODUCTION: The most widely used method for measuring free @entity251 (FT) is by analog immunoassay (aFT); however, this assay has been criticized as unreliable based on laboratory studies in small groups of @entity1 . Calculated FT (cFT), derived from total @entity251 (TT) and @entity443 ( @entity443 ) values has been recommended in its place. There are limited data comparing aFT and cFT in clinical populations. AIM: The purpose of this study was to compare aFT with cFT in a population of ambulatory @entity1 in a clinical setting. METHODS: Medical records were reviewed for 100 randomly selected @entity1 in a urology practice, yielding 140 test results complete for TT, aFT, and @entity443 . Calculated FT was determined via an online calculator. Comparisons were made with @entity6632 . MAIN OUTCOME MEASURES: Pearson rank correlation between aFT and cFT. RESULTS: Mean @entity1 age was 52.3 +/- 14.3 years (range 24-80). Mean TT was 443.0 +/- 208.3 ng/dL (range 110-1276). Mean aFT was 1.22 +/- 0.54 ng/dL (range 0.24-3.8) and mean cFT 9.4 +/- 4.5 ng/dL (range 1.8-27.8). Mean @entity443 was 34.2 +/- 19.5 nmol/L (range 9-127). A strong correlation was observed for aFT and cFT (r = 0.88, P < 0.0001), particularly at low concentrations. Significant correlations were also noted between aFT and TT (r = 0.73, P < 0.0001), and between cFT and TT (r = 0.82, P < 0.0001). Numerical values for aFT were approximately one-eighth of the values obtained for cFT. Neither aFT nor cFT correlated with @entity443 . CONCLUSIONS: A strong correlation was observed between aFT and cFT in this clinical population of ambulatory @entity1 . Different sets of reference values must be applied for each of these tests.
