Cy-TB Test Identifies Latent Tuberculosis in Dialysis Patients, Study Finds
A single-center study of 95 chronic kidney disease patients on hemodialysis found the Cy-TB skin test agreed completely with standard IGRA testing for latent tuberculosis, with an overall prevalence of 4.2%. Early dialysis phase (<6 months) was a strong predictor of positivity, suggesting a potential priority screening window, though larger confirmatory studies are needed.
A study has found that the Cy-TB skin test shows perfect agreement with interferon-gamma release assay (IGRA) for detecting latent tuberculosis infection (LTBI) in chronic kidney disease patients on maintenance hemodialysis, with an overall prevalence of just 4.2% — far lower than the 15–25% reported in prior international dialysis cohorts.
The hospital-based cross-sectional study, published in Cureus, enrolled 95 consecutive CKD patients on hemodialysis. All participants underwent Cy-TB testing with induration measurement at 48–72 hours; positive cases were confirmed by the IGRA reference test.
The overall LTBI prevalence was 4.2% (4 out of 95; 95% CI: 1.2%–10.3%). Dialysis duration of less than six months emerged as the strongest independent predictor of Cy-TB positivity (p=0.001; odds ratio 13.5; 95% CI: 2.5–72.8), with 75% of all positive cases occurring within this early dialysis phase. The prevalence in the early-phase subgroup was 17.6%, compared to just 1.3% among those on dialysis for six months or longer.
A prior history of tuberculosis was also significantly associated with increased positivity risk (p=0.048; OR 25.2; 95% CI: 1.4–442.8). Urban residence, presence of comorbidities, and elevated fever showed only marginal associations, while age, gender, BMI, smoking, alcohol use, TB contact history, and respiratory symptoms were not significant.
Among the four LTBI-positive cases, the Cy-TB test showed perfect agreement with IGRA; however, the researchers caution that this finding is based on a very small number of events and should be interpreted cautiously. They conclude that the early dialysis phase could represent a priority window for LTBI screening, but emphasize that the findings are exploratory and require confirmation in larger, comparative, and longitudinal studies.
Latent tuberculosis infection affects approximately one-quarter of the global population, with an estimated 5–10% of cases progressing to active disease, a risk that is substantially higher in immunocompromised individuals such as those with chronic kidney disease. Early identification and treatment of LTBI can reduce progression by about 60%. The World Health Organization reported 10.7 million new TB cases and 1.23 million TB-related deaths globally in 2024, with India carrying 26% of the global burden.