Omics-Based Sperm-Retrieval Prediction in Non-Obstructive Azoospermia: A Critical Narrative Review and Validation Framework.

In non-obstructive azoospermia (NOA), microdissection testicular sperm extraction can provide sperm for intracytoplasmic sperm injection, but retrieval fails in approximately half of procedures. Genomic, transcriptomic, noncoding RNA, proteomic, metabolomic, and microbiome studies have reported molecular associations and prediction estimates. This critical narrative review examines the requirements for an assay-model system to support preoperative retrieval counseling. A focused PubMed/MEDLINE search updated on 31 August 2026 and targeted reference checking identified representative human reports and methodological guidance. Selected reports mainly illustrate discovery, development, and same-source evaluation. Common limitations include small cohorts, local assay optimization, heterogeneous outcomes, incomplete calibration, and uncertain transportability. Established karyotyping and Y-chromosome testing must be distinguished from discovery-scale genomics, which currently supports etiologic and qualified genotype-specific counseling rather than a universal calibrated retrieval model. A routine-variable multicenter model reported an external-cohort area under the receiver-operating-characteristic curve (AUC) of 0.8301, although cohort provenance, calibration, and clinical utility require independent confirmation. An author-developed seven-gate framework integrates clinical-question definition, assay specification, model development, internal validation, external evaluation, incremental value, and prospective impact. Future omics studies should test incremental value beyond a prespecified routine-variable model in the same patients and assess calibration, threshold consequences, net benefit, assay failure, cost, and patient outcomes.