Elsevier

Kidney International

Volume 65, Issue 5, May 2004, Pages 1826-1834
Kidney International

Clinical Nephrology – Epidemiology – Clinical Trials
Tuberculin skin testing underestimates a high prevalence of latent tuberculosis infection in hemodialysis patients

https://doi.org/10.1111/j.1523-1755.2004.00586.xGet rights and content
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Tuberculin skin testing underestimates a high prevalence of latent tuberculosis infection in hemodialysis patients.

Background

Identification of latent Mycobacterium tuberculosis infection in hemodialysis patients is hampered by reduced sensitivity of the established tuberculin skin test. We investigated whether in vitro quantitation of purified protein derivative (PPD)–specific T cells using a rapid 6-hour assay may represent an alternative approach for detecting latent infection.

Methods

One hundred and twenty-seven hemodialysis patients and 218 control patients (blood donors, health care workers, and control patients) were analyzed. Specific T cells toward PPD and early secretory antigenic target-6 (ESAT-6), a protein expressed in Mycobacterium tuberculosis but absent from M. bovis bacillus Calmette-Guerin (BCG) vaccine strains, were flow cytometrically quantified from whole blood, and results were compared with skin testing.

Results

Compared to blood donors, a high proportion of both health care workers (48.6%) and hemodialysis patients (53.5%) had PPD-specific Th1-type CD4 T-cell reactivity with similar median frequencies of PPD-specific T cells (0.17%; 0.06–3.75% vs. 0.26%; 0.06–4.12%, respectively). In contrast, skin test reactivity was significantly reduced in hemodialysis patients. Whereas 85.7% of control patients with PPD reactivity in vitro were skin test–positive, the respective percentage among hemodialysis patients was 51.4% (P = 0.007). Among individuals with PPD reactivity in vitro, ∼50% had T cells specific for ESAT-6.

Conclusion

Unlike the skin test, measurement of PPD reactivity by in vitro quantitation of PPD-specific T cells was unaffected by uremia-associated immunosuppression. This whole-blood assay may thus be a valuable alternative to skin testing, and detection of ESAT-6–specific T cells could moreover allow distinction of latent M. tuberculosis infection from BCG-induced reactivity to PPD. The assay is well suited for clinical use and may facilitate targeting of preventative therapy in high-risk individuals.

Keywords

latent tuberculosis infection
T-cell response
flow cytometry
tuberculin skin test
hemodialysis
immunodeficiency

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