Total testosterone assays in women with polycystic ovary syndrome: precision and correlation with hirsutism

Abstract

Context: There is no standardized assay of testosterone in women. Liquid chromatography mass spectrometry (LC/MS) has been proposed as the preferable assay by an Endocrine Society Position Statement.

Objective: The aim was to compare assay results from a direct RIA with two LC/MS.

Design and setting: We conducted a blinded laboratory study including masked duplicate samples at three laboratories--two academic (University of Virginia, RIA; and Mayo Clinic, LC/MS) and one commercial (Quest, LC/MS).

Participants and interventions: Baseline testosterone levels from 596 women with PCOS who participated in a large, multicenter, randomized controlled infertility trial performed at academic health centers in the United States were run by varying assays, and results were compared.

Main outcome measure: We measured assay precision and correlation and baseline Ferriman-Gallwey hirsutism scores.

Results: Median testosterone levels were highest with RIA. The correlations between the blinded samples that were run in duplicate were comparable. The correlation coefficient (CC) between LC/MS at Quest and Mayo was 0.83 [95% confidence interval (CI), 0.80-0.85], between RIA and LC/MS at Mayo was 0.79 (95% CI, 0.76-0.82), and between RIA and LC/MS at Quest was 0.67 (95% CI, 0.63-0.72). Interassay variation was highest at the lower levels of total testosterone (≤50 ng/dl). The CC for Quest LC/MS was significantly different from those derived from the other assays. We found similar correlations between total testosterone levels and hirsutism score with the RIA (CC=0.24), LC/MS at Mayo (CC=0.15), or Quest (CC=0.17).

Conclusions: A testosterone RIA is comparable to LC/MS assays. There is significant variability between LC/MS assays and poor precision with all assays at low testosterone levels.

Trial registration: ClinicalTrials.gov NCT00068861.

Figures

Figure 1

Median levels of serum testosterone from women with PCOS measured by the three different methods (RIA at UVA lab, and LC/MS at Quest and Mayo). Line within the box represents the median, lower boundary of box indicates the 25th percentile, and the upper boundary of box indicates the 75th percentile. Whiskers above and below indicate the maximum and minimum testosterone values.

Figure 2

A–C, Deming regression plots of serum testosterone concentrations in women with PCOS measured in duplicate (using masked samples) by assay type. D–F, Plots of absolute percentage differences in serum testosterone levels between the duplicate samples by assay. The bold solid line represents 0%; the light solid line, the mean percentage difference between the methods; and the dashed line, 2 sd values of the absolute mean percentage difference.

Figure 3

Deming regression plots and regression equations of all samples for serum testosterone concentrations in women with PCOS. A, Quest LC/MS vs. Mayo LC/MS; B, Quest LC/MS vs. UVA RIA; C, Mayo LC/MS vs. UVA RIA.

Figure 4

Bland-Altman plots of percentage differences in serum testosterone levels (test minus LC-MS/MS or RIA) in women with PCOS against the average of the two methods. The bold solid line represents 0%; the light solid line, the mean percentage difference between the methods; and the dashed lines, 2 sd of the mean percentage difference.

Figure 5

Deming regression plots of total testosterone levels in women with PCOS and baseline Ferriman-Gallwey Hirsutism score.