Polycystic ovary syndrome (PCOS) is an endocrine disorder including polycystic ovarian morphology (PCOM). Anti-Müllerian hormone (AMH) levels correlate with the number of follicles (TFC) in the ovary. In PCOS, this is reflected by increased AMH levels and therefore AMH is suggested as a proxy for PCOM. However, lack of a golden standard has led to inter-assay variability. In addition, little is known about the inter-assay correlation in PCOS. Hence, this study aims to investigate the correlation between different AMH assays and TFC in PCOS patients. 

 AMH levels were measured in 1660 PCOS patient by three different assays: (1) Modified Gen II AMH ELISA; (2) picoAMH assay; and (3) Automated Elecsys AMH plus. Patients were divided in three subgroups: low (<2.80 ng/ml), mid (2.80–7.04 ng/ml) and high AMH level (>7.04 ng/ml). Passing Bablok regression was used for the comparison between assay methods. Spearman’s rank was used to assess the correlation between AMH and TFC.

 The inter-assay correlations over the total range of AMH levels were: Gen II vs Elecsys: 0.81; picoAMH vs Gen II: 0.81; picoAMH vs Elecsys: 0.94. Stratification in subgroups revealed an AMH level dependent inter-assay correlation. A strong inter-assay correlation was present in both the low and high AMH subgroups, ranging from 0.62–0.86. The correlation in the mid AMH level subgroup was moderate, with coefficients ranging between 0.28–0.56.

A positive correlation was present between AMH levels and TFC, with correlation values ranging from 0.57–0.62. Subgroup analysis showed that only in patients with low AMH levels, the correlation with follicle count was moderate (0.36–0.55). With AMH levels above 2.80 ng/ml the correlation with follicle count decreased independent of the assay with correlations between 0.18–0.38.

In conclusion, in our cohort of PCOS patients both the inter-assay correlation and the correlation between AMH level and follicle count depend on range of serum AMH level. This once more emphasizes the need of a standardization of AMH measurement for an accurate interpretation of AMH.