Clinical Relevance of Interferon-Gamma Release Assay versus Tuberculin Skin Testing for Diagnosis of Latent Tuberculosis in Chronic Hemodialysis Patients .

There is no gold standard method for detecting latent tuberculosis infection (LTBI) in end stage renal disease (ESRD), the use of tuberculin skin test(TST) remains controversial due to its high rate of false results, new interferon gamma release assays have been developed for diagnosing LTBI as the QuantiFERON-TB Gold test(QFT-G).

The aim of this work was to evaluate the value of Quantiferon-TB Gold test and compare its performance with tuberculin skin test in the diagnosis of latent tuberculosis infection among ESRD patients receiving hemodialysis(HD).

Patients and Methods: 60 ESRD patients undergoing HD and 40 healthy controls were subjected to TST and QFT-G to diagnose Latent TB infection.

Results: QFT-G and TST were positive in 31.7 % and 45 % of patients respectively. The overall agreement was 73.3% (statistically significant with moderate agreement, p=0.001 & k=0.44), while it was 70% in BCG vaccinated patients (statistically significant with fair agreement, p=0.003 & k=0.37) and 80% in non BCG vaccinated patients (statistically significant with moderate agreement, p=0.001 & k=0.56). There were no statistically significant differences between patients and controls as regards age, sex, duration of hemodialysis and history of contact to known TB patients.

Conclusion: We conclude that QFT-G test shows overall moderate agreement with TST and it could be used in screening of LTBI in ESRD patients simultaneously with TST and QFT-G test is more specific and accurate than TST in BCG vaccinated patients as BCG vaccination reduces their agreement, increasing the risk of TST false positive results rather than QFT-G positivity but relatively high cost and need for laboratory instruments is a limitation of QFT-G test