Late HIV Presentation Remains High in Korea: 28-Year National Surveillance Trends and the Limits of Inference under Incomplete CD4 Capture, 1998-2025.

Background

Whether late human immunodeficiency virus (HIV) presentation in Korea has improved is difficult to judge because a CD4 count at diagnosis was captured for only a minority of notified cases until 2025. We examined 28-year trends in late presentation (CD4 <350 cells/µL) and advanced HIV disease (AHD; CD4 <200 cells/µL) among cases with a captured CD4 result, quantified how incomplete and time-varying capture limits inference about population-level trends, and characterized the burden in 2025, the year of highest CD4 capture (80.4%).

Materials And Methods

We analyzed national HIV/acquired immunodeficiency syndrome (AIDS) notification data from the Korea Disease Control and Prevention Agency (1998-2025). Annual proportions among captured cases were modeled with overdispersion-adjusted logistic regression and adjusted for mean age and for the annual uncaptured fraction; change-points were identified by joinpoint regression. Missing CD4 values were treated as incomplete capture; distribution-free Manski bounds were computed for every year, with a missing-not-at-random tipping-point analysis and a sensitivity analysis for recent infection.

Results

Among captured cases, late presentation showed no significant change (odds ratio [OR] per year, 1.008; 95% confidence interval [CI], 0.995-1.021; P=0.259) and the AHD proportion increased (OR per year, 1.027; 95% CI, 1.012-1.042; P<0.001), independent of age. These captured-only trends cannot be read as population-level trends: the uncaptured fraction was 0.40-0.83 before 2025, so the Manski bounds do not identify the direction of any trend, and adjusting for the uncaptured fraction (OR per 0.10 increase, 1.059 and 1.062) did not attenuate the year effect. The decrease in the AHD proportion after 2022 coincided with an abrupt increase in capture (uncaptured fraction, 0.83 to 0.20). In 2025, late presentation was 0.596 among captured cases (Manski bounds, 0.480-0.675) and AHD was 0.379 (0.305-0.501); both intervals contain the 2013-2015 Korea HIV/AIDS Cohort estimates (0.564 and 0.356). Reclassifying up to half of recent infections (27.3% of diagnoses) as not late left the 2025 late-presentation proportion at ≥0.460.

Conclusion

In 2025, approximately half to two-thirds of new HIV diagnoses in Korea were late and one-third to one-half had advanced disease, above contemporary European levels and far above the World Health Organization European target. Whether this burden has improved cannot be determined from surveillance data, because captured-only trends track the completeness of CD4 capture. Late-presentation indicators should be reported together with capture completeness, and cohort data with complete CD4 ascertainment are needed to establish the trend.