Using CA-62 Marker in a Pilot Screening Project in Kazakhstan, 2021: Baseline Data and Scenario-Based Modeling of Estimated Specificity

The CLIA-CA-62 assay is an in vitro diagnostic device registered in Russia and Kazakhstan for measuring a marker specific to epithelial carcinomas. This pilot project aimed to assess CA-62 utility for primary cancer screening in an asymptomatic cohort in Kazakhstan. The trial was interrupted in January 2022 for reasons unrelated to the scientific program before clinical outcomes could be obtained. Available baseline data were therefore used to characterize the CA-62 value distribution and perform a scenario-based assessment of estimated assay specificity at a reference value of 5,000 U/mL. The analysis included 1,214 quantitative CA-62 measurements from asymptomatic healthcare workers aged 45–70 years, collected during annual preventive examinations between September and October 2021. The distribution was markedly right-skewed, with 92.5% of samples in the normal zone (median: 3,371 U/mL; IQR: 1,965–4,415 U/mL; 95th percentile: 6,309 U/mL). At the 5,000 U/mL cutoff, 7.5% of results (91/1,214) were elevated. Scenario-based modeling assuming cancer prevalence of 0.5–2.5% and assay sensitivity of 65–95% yielded an estimated specificity of 92.79–94.75%. These findings provide an analytical foundation for prospective verification of CA-62 in primary screening settings.