Anti-Mullerian Hormone-to-Testosterone Ratio is Predictive of Positive Sperm Retrieval in Men with Idiopathic Non-Obstructive Azoospermia

Abstract

The lack of clinically-reliable biomarkers makes impossible to predict sperm retrieval outcomes at testicular sperm extraction (TESE) in men with non-obstructive azoospermia (NOA), resulting in up to 50% of unnecessary surgical interventions. Clinical data, hormonal profile and histological classification of testis parenchyma from 47 white-Caucasian idiopathic NOA (iNOA) men submitted to microdissection TESE (microTESE) were analyzed. Logistic regression analyses tested potential clinical predictors of positive sperm retrieval. The predictive accuracy of all variables was evaluated using the receiver operating characteristic-derived area under the curve, and the clinical net benefit estimated by a decision-curve analysis (DCA). Overall, 23 (49%) and 24 (51%) patients were classified as positive and negative sperm retrievals at microTESE. While circulating hormones associated to a condition of primary hypogonadism did not predict sperm retrieval, levels of anti-Mullerian hormone (AMH) and the ratio AMH-to-total Testosterone (AMH/tT) achieved independent predictor status for sperm retrieval at microTESE, with a predictive accuracy of 93% and 95%. Using cutoff values of <4.62 ng/ml for AMH and <1.02 for AMH/tT, positive sperm retrieval was predicted in all individuals, with 19 men out of 47 potentially spared from surgery. DCA findings demonstrated clinical net benefit using AMH and AMH/tT for patient selection at microTESE.

Figure 1

Serum levels of AMH and AMH/tT ratio values did not allow to stratifying histological classification of human spermatogenesis. (A,B) Descriptive classification of human spermatogenesis was performed using Johnsen’s (43) and McLachlan’s (42) score. Score for assessing spermatogenesis in testicular biopsy according to the Johnsen score: 10 = complete spermatogenesis and perfect tubules; 9 = many spermatozoa present but disorganized spermatogenesis; 8 = few spermatozoa present; 7 = no spermatozoa but many spermatids present; 6 = few spermatids present; 5 = nospermatozoa or spermatids present but many spermatocytes present; 4 = few spermatocytes present; 3 = only spermatogonia present; 2 = no germ cells present; 1 = neither germ cells nor Sertoli cells present. Score for assessing spermatogenesis in testicular biopsy according to the McLachlan score: 1 = normal testicular biopsy, full spermatogenesis in the entire biopsy and the presence of a normal inter-tubular tissue; 2 = hypospermatogenesis, when all stages of spermatogenesis are present but reduced to a varying degree, including varying patterns that can result in some tubules showing an epithelium containing Sertoli cells only; 3 = germ cell arrest, describes the total arrest at a particular stage, most often at the spermatogonial or primary spermatocyte stage; 4 = Sertoli cell only syndrome, when there are no tubules containing germ cells. Dot plots depict AMH levels and AMH/tT ratio values from the 23 positive sperm retrievals and 24 negative sperm retrievals; horizontal bars detail median values. Dashed lines represent the range of reference values for AMH levels. Lack of statistical significance among classes was evaluated by ANOVA. (C,D) Classification of testis parenchyma based on hyperplasia of Leydig cells. Dot plots show values from the 23 positive sperm retrievals and 24 negative sperm retrievals iNOA men; horizontal bars detail median values. Dashed lines represent the range of reference values for AMH levels. Lack of statistical significance between classes was evaluated by two-tail unpaired T test.

Figure 2

Circulating AMH levels and AMH/tT ratio values were predictive of sperm retrieval in iNOA men undergoing microTESE. (A,B) Dot plots depict values from the 23 positive sperm retrievals and 24 negative sperm retrievals iNOA men; horizontal bars detail median values. Dashed lines represent the range of reference values for the serum level of AMH. Statistical significance was evaluated by means of two-tail non-parametric T test (Mann-Whitney test). (C,D) ROC-derived curve, showing the AUC (Area Under the Curve) 95% CI (confidence intervals) and statistical significance. (E) Decision curve analysis showing the net benefit of AMH and AMH/tT on the prediction of positive sperm retrieval in iNOA men undergoing to microTESE. The use of the cutoff of <4.62 ng/ml for AMH and of <1.02 for AMH/tT resulted in positive net benefit; in the absence of any marker the 50% probability of sperm retrieval was associated to a net benefit of 0, whereas the use of the 2 markers at the threshold of 50% provided increased net benefit to 0.3–0.4, with the AMH/tT ratio scoring better than AMH.