Calprotectin as a novel diagnostic approach to screen male infertility risk: A pilot study

Diagnosis of male infertility is essentially based on the evaluation of semen quality (sperm concentration, motility, viability, and morphology). However, there is a lack of knowledge about possible molecules used as candidates for the early identification of male infertility risk. Calprotectin is a biological marker for inflammation, measured prevalently in stool specimens, widely used to discriminate between inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), and for the subsequent monitoring of gastrointestinal diseases' development. Would it be possible to use calprotectin determination to identify also male infertility risk?

Cross-sectional pilot study investigated calprotectin concentration in the seminal fluid of 45 men (range: 23-51 yrs) that were under evaluation for semen quality at our Center for Reproductive Medicine. Calprotectin concentration was determined with a commercially available immuno-chromatographic test and successfully detected in 37 of the 45 analyzed men (age: 37.38 ± 6.59). A correlation with semen quality (concentration, motility, morphology) was assessed.

Higher calprotectin concentration seemed to indicate a better quality of the seminal fluid. Normozoospermic subjects (Group A) had on average a calprotectin value of 0.215 ± 0.162 µg/ml (mean ± SD), while subjects with at least one of the semen parameters below reference values (Group B) showed lower calprotectin concentration (mean ± SD: 0.126 ± 0.068, p-value < 0.05). A significant difference was clearly evident between calprotectin concentration measured in seminal fluids with physiological sperm morphology (≥4%) as compared with teratozoospermic samples (<4%) (p-value < 0.05). Indeed, the developed ROC curves showed a good diagnostic accuracy (around 67 %) using calprotectin concentration (threshold value: 0.121 μg/ml) as a preliminary test to discriminate subjects with and without abnormal semen parameters, especially morphology.

Calprotectin determination in the seminal fluid may be proposed as a biological marker for preliminary screening in male subjects at risk of infertility due to one or more alterations of semen quality.