Testicular Immune Privilege Maintained in Incidental Testicular Microlithiasis: Evidence from 1755 Infertile Men

In 1,755 infertile men, testicular microlithiasis was not associated with higher antisperm antibody rates (1.2% vs 3.5%, p=0.17)

Journal: Journal of Reproductive Immunology | Published: 2026-02-06 | Type: Retrospective cohort | PMID: 41666654 Authors: Tienforti D, Spagnolo L, Cordeschi G, Baroni MG, Barbonetti A (Andrology Unit, University of L'Aquila, Italy) Funding/COI: Funding not listed. Authors declare no competing financial interests.

Summary

Testicular microlithiasis (TM) — calcium deposits visible on scrotal ultrasound — has long been suspected of disrupting the testis's immune privilege and triggering antisperm antibody (ASA) production. This retrospective study of 1,755 infertile men found the opposite: ASA positivity was actually numerically lower in TM men than non-TM men, and the difference was not statistically significant. The authors argue there is no basis for routinely testing ASA in men with incidentally discovered TM.

Claims

• TM was present in 167 of 1,755 infertile men (9.5%)
• ASA positivity (≥50% IgG MAR binding) occurred in 1.2% of TM men vs. 3.5% of non-TM men (p = 0.17)
• Semen parameters (concentration, motility, morphology) were comparable between TM and non-TM groups
• Prior orchiectomy was more frequent in the TM group — a known ASA risk factor that could confound in the opposite direction
• Authors describe this as the largest cohort to date evaluating TM and ASA

Study Quality

This is a retrospective cohort spanning 21 years (2001–2022) at a single andrology unit. The sample size of 1,755 is substantial for this niche question, and the 167 TM cases are enough to draw meaningful conclusions about ASA prevalence. ASA measurement used the direct IgG MAR test with a clinically accepted threshold (≥50% binding), which is a reasonable standardized method.

The retrospective single-center design limits generalizability. The 21-year span introduces heterogeneity in ultrasound equipment, operator technique, and clinical protocols across time. The abstract does not report whether the analysis adjusted for covariates — notably, the TM group had more prior orchiectomies, which itself elevates ASA risk, meaning any true signal from TM could have been masked by this imbalance.

Red Flags

• Single-center, retrospective design — selection bias is inherent (all men were already presenting for infertility evaluation)
• No covariate adjustment reported in the abstract; the orchiectomy imbalance is acknowledged but it's unclear how it was handled analytically
• Funding source not disclosed — minor concern given the null finding, but worth noting
• p = 0.17 with a numerical difference (1.2% vs 3.5%) still leaves room for a real effect the study was underpowered to detect at the subgroup level
• The study population is exclusively infertile men; results may not generalize to men with TM found incidentally in fertility-normal contexts

Strengths

• Largest cohort to date for this specific question
• Long follow-up window (2001–2022) and consistent institutional protocol
• Standardized ASA measurement with a clinically accepted threshold
• Authors acknowledge the orchiectomy imbalance as a limitation, suggesting awareness of the confound
• The null finding is clinically actionable: it argues against a low-yield, costly reflex test

Verdict

A well-powered retrospective study that delivers a clean null finding on a genuinely contested hypothesis. The biology was plausible — TM was thought to breach the blood-testis barrier — but the data from 1,755 men don't support it, at least not at the level of measurable immune activation. The lack of adjusted analyses is a real methodological gap, and the single-center retrospective design means this shouldn't be the last word. But as evidence against reflexively ordering ASA panels in men with incidental TM on ultrasound, this is the best available data. Clinically useful, methodologically honest, appropriately modest.