New data demonstrates that relationship of salivary to serum progesterone in Bolivian women is comparable to that in other populations

Abstract

Abstract. Salivary progesterone (P) concentration is widely used in field studies as a relatively easy-to-measure proxy for serum P. Chatterton et al. [Fertility & Sterility 86:723 (2006)] compared sample means of salivary and serum P in concurrent samples taken during the putative luteal phase from women in La Paz, Bolivia (n526) and Chicago, USA (n520). They concluded that salivary/serum P ratios (hereinafter ‘‘uptake fractions’’) vary significantly among populations (precluding crosspopulational comparisons of salivary P), and that salivary P may not be a reliable proxy for serum P in Bolivian and other non-industrialized populations. We have previously disputed this claim [AJHB 21:271 (2008)], arguing that sample contamination and/or assay errors are more plausible explanations for Chatterton et al.’s data. Here we report analyses of new data collected specifically to investigate the relationship of salivary P 280 ABSTRACTS to serum P in Bolivian women. Simultaneous saliva/serum samples (n572) from 36 women were collected approximately one and three weeks following the preceding menses; samples were subsequently assigned to an ovarian-cycle phase based on the date of the subsequent menses. As did Chatterton et al., here we focus on the luteal-phase data. We find an excellent correlation (r50.78) between salivary and serum P in these samples, with uptake fractions typically around 3%, similar to published reports of this ratio in other populations. We conclude that salivary P is a reliable proxy for serum P in Bolivian women and (assuming comparable assays) that comparisons of salivary P are valid across populations.