Association of CKD with incident TB

Who

• Adults in South Korea (≥19 years) enrolled in the National Health Insurance Service (NHIS) screening program.

• 408,873 people with predialysis CKD (stages 1–5 not on dialysis), each matched 1:1 to 408,873 controls without CKD by age, sex, smoking history, and low-income status (total ≈ 817,746 participants).

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What

• Focus: To assess whether predialysis CKD (not yet on dialysis or transplanted) is associated with higher risk of incident active tuberculosis (TB), and to examine short-term mortality after TB.

• Main findings:

  • Incidence of active TB was higher in predialysis CKD vs matched controls:

    • CKD: 1704 TB cases; 137.5 per 100,000 person-years

    • Controls: 1518 TB cases; 121.9 per 100,000 person-years

    • Adjusted hazard ratio (HR) for active TB with CKD: 1.21 (95% CI 1.13–1.30).

  • By CKD stage (vs controls, fully adjusted):

    • Stage 1 (eGFR ≥90 + albuminuria): HR ≈ 1.82

    • Stage 2 (eGFR 60–89 + albuminuria): HR ≈ 1.19 (borderline)

    • Stage 3 (eGFR 30–59): HR ≈ 1.16

    • Stage 4/5 without dialysis (eGFR <30): HR ≈ 1.85.

  • CKD was associated with higher risks of pulmonary, non-pulmonary, and miliary TB.

  • Among those who developed TB, 1-year all-cause mortality was higher in the CKD group (adjusted HR 1.68; 95% CI 1.28–2.22).

• Authors’ conclusion: Predialysis CKD is associated with increased incidence of active TB and worse short-term prognosis after TB. Particular concern is warranted for CKD stage 1 and advanced CKD (stages 4/5) not on dialysis.

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When

• Health screenings to define CKD status: 2012–2016.

• Follow-up for TB events and mortality: from each participant’s index examination date until TB, death, or December 31, 2016.

• Median follow-up: about 3.0 years in both CKD and control groups.

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Where

• Republic of Korea, using the nationwide National Health Insurance Database (NHID) and its general health screening program.

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Why

• CKD prevalence is increasing globally and in countries where TB remains endemic.

• Dialysis and kidney transplantation are known TB risk factors, but large-scale data on TB risk in predialysis CKD were lacking.

• Because CKD is associated with immune dysfunction and infection risk, the authors aimed to clarify if earlier CKD stages already confer significantly increased TB risk to guide surveillance and management.

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How

• Design: Nationwide retrospective population-based cohort study.

• Data source: Korean NHID, including:

  • General health screening data (serum creatinine, urine dipstick albuminuria, BMI, smoking, etc.).

  • Claims data with mandatory TB insurance codes and ICD-10 diagnoses to identify active TB (A15–A19).

• Population definition:

  • Included adults with ≥2 health screenings (2012–2016) using Jaffe-based creatinine.

  • Predialysis CKD: persistent CKD indicators (eGFR <60 mL/min/1.73 m² and/or dipstick albuminuria ≥1+) in two or more consecutive screenings.

  • Excluded those with prior TB, prior kidney replacement therapy, fluctuating/transient CKD labs, or (for controls) any CKD codes.

• Exposure: Presence and stage of predialysis CKD, categorized per KDIGO into stages 1, 2, 3, and 4/5 (non-dialysis) using baseline eGFR and albuminuria.

• Outcome measures:

  • Primary: Incident active TB (pulmonary, non-pulmonary, miliary) during follow-up.

  • Secondary: TB-associated mortality, defined as 1-year all-cause death after TB diagnosis.

• Analysis:

• 1:1 matching of CKD patients to controls by age, sex, smoking history, and low-income status.

• Incidence rates calculated per 100,000 person-years.

• Cox proportional hazards models with:

  • Model 1: adjusted for matching factors.

  • Model 2: additionally adjusted for BMI, residence (urban/rural), diabetes, hypertension, cancer, COPD, immunosuppressant use.

• Subgroup analyses by CKD stage and TB site; risk factor analysis for TB within the CKD cohort using multivariable Cox with backward elimination.

Source: Park, S., Lee, S., Kim, Y., Lee, Y., Kang, M.W., Cho, S., Han, K., Han, S.S., Lee, H., Lee, J.P. and Joo, K.W., 2019. Association of CKD with incident tuberculosis. Clinical Journal of the American Society of Nephrology, 14(7), pp.1002-1010.