A retrospective review of the two-step tuberculin skin test in dialysis patients.
BACKGROUND
Reactivation of latent Mycobacterium tuberculosis infection (LTBI) is a health concern for patients on dialysis or receiving a kidney transplant, as these patients are often immunosuppressed. The most frequently used test for LTBI screening in this population is the tuberculin skin test (TST). The diagnostic accuracy (sensitivity and specificity) of the TST in a contemporary North American or Western European dialysis population is unknown.


OBJECTIVE
Our objective was to determine the diagnostic accuracy and clinical utility of the two-step TST in patients receiving dialysis.


METHODS
This is a retrospective cohort study.


METHODS
This study is set at four tertiary dialysis units across Winnipeg, Manitoba.


METHODS
There are 483 chronic hemodialysis and peritoneal dialysis patients in the study.


METHODS
The measurements are sensitivity and specificity of the TST with respect to abnormal chest X-ray.


METHODS
All patients received a two-step TST and assessment of risk factors for prior tuberculosis (TB) infection between February 2008 and December 2008. This cohort was retrospectively linked to our tuberculosis registry to ascertain if prophylaxis was received for LTBI.


RESULTS
At an induration cutoff of 5 mm, 62 (13 %) patients had a positive two-step TST. Patients with a known Bacillus Calmette-Guérin (BCG) vaccination were more likely to test positive (50 % of those with a positive TST had a BCG versus 34 % with a negative TST, p = 0.05). Using a diagnostic gold standard of an abnormal chest X-ray as a proxy for LTBI, the sensitivity of the TST was only 14 % and the specificity was 88 %. Only 8 of 62 patients with a positive TST (13 %) received prophylaxis for LTBI. None of the patients who tested negative were treated.


CONCLUSIONS
There is a lack of a truly accurate gold standard for LTBI.


CONCLUSIONS
The TST has limited diagnostic and clinical utility for LTBI screening in patients on dialysis. Further research into the diagnostic accuracy of interferon-gamma release assays and a revision of LTBI screening guidelines in patients on dialysis should be considered.
Seven Oaks General Hospital Renal Program, 2PD12 - 2300 McPhillips Street, Winnipeg, MB R2V 3M3 Canada ; Department of Medicine, University of Manitoba, Winnipeg, Canada.
Rukhsana
R
Foster
Seven Oaks General Hospital Renal Program, 2PD12 - 2300 McPhillips Street, Winnipeg, MB R2V 3M3 Canada ; Chronic Disease Innovation Centre, Seven Oaks General Hospital, Winnipeg, Canada ; Department of Medicine, University of Manitoba, Winnipeg, Canada.
Thomas W
TW
Ferguson
Seven Oaks General Hospital Renal Program, 2PD12 - 2300 McPhillips Street, Winnipeg, MB R2V 3M3 Canada ; Chronic Disease Innovation Centre, Seven Oaks General Hospital, Winnipeg, Canada ; Department of Medicine, University of Manitoba, Winnipeg, Canada.
Claudio
C
Rigatto
Seven Oaks General Hospital Renal Program, 2PD12 - 2300 McPhillips Street, Winnipeg, MB R2V 3M3 Canada.
Blake
B
Lerner
Seven Oaks General Hospital Renal Program, 2PD12 - 2300 McPhillips Street, Winnipeg, MB R2V 3M3 Canada ; Chronic Disease Innovation Centre, Seven Oaks General Hospital, Winnipeg, Canada ; Department of Medicine, University of Manitoba, Winnipeg, Canada.
Navdeep
N
Tangri
Seven Oaks General Hospital Renal Program, 2PD12 - 2300 McPhillips Street, Winnipeg, MB R2V 3M3 Canada ; Chronic Disease Innovation Centre, Seven Oaks General Hospital, Winnipeg, Canada ; Department of Medicine, University of Manitoba, Winnipeg, Canada.
Paul
P
Komenda
Chronic renal failure; Dialysis; End-stage renal disease; Immunosuppression; Kidney transplantation; Latent tuberculosis infection; Tuberculin skin test; Tuberculosis