title: Comparison of T-Spot.TB and tuberculin skin test among silicotic patients.
abstract: In the present study, T-Spot.TB and the tuberculin skin test (TST) were compared in the screening of latent tuberculosis infection among silicotic patients. A conditional probability model was used to compare the potential clinical utilities of T-Spot.TB and TST performed on 134 silicotic subjects from December 1, 2004 to January 31, 2007. Data from a historical cohort were also reanalysed for further comparison. Agreement with T-Spot.TB was best using a TST cut-off of 10 mm. Age >or=65 yrs independently predicted a tuberculin reaction <10 mm (odds ratio = 3), but not a negative T-Spot.TB response. Lower measures of agreement were observed among current smokers and those aged >or=65 yrs. Tuberculin reaction size was well correlated with both early secretary antigenic target 6 and culture filtrate protein 10 spot counts, except among current smokers. Within the current estimates of sensitivity (88-95%) and specificity (86-99%) for T-Spot.TB, the positive likelihood ratio for T-Spot.TB test would be substantially higher (6.29-95.0 versus 1.65-1.94) and negative likelihood ratio substantially lower (0.05-0.14 versus 0.32-0.41) than the corresponding ratios for the tuberculin test. A low tuberculosis risk differential was similarly observed between tuberculin-negative and untreated tuberculin-positive subjects in the historical cohort. T-Spot.TB is likely to perform better than tuberculin test in the screening of latent tuberculosis infection among silicotic subjects.
authors.affiliation: Tuberculosis and Chest Service, Centre for Health Protection, Dept of Health, University of Hong Kong, China. cc_leung@dh.gov.hk
authors.forename: C C
authors.initials: CC
authors.lastname: Leung
authors.forename: W C
authors.initials: WC
authors.lastname: Yam
authors.forename: W W
authors.initials: WW
authors.lastname: Yew
authors.forename: P L
authors.initials: PL
authors.lastname: Ho
authors.forename: C M
authors.initials: CM
authors.lastname: Tam
authors.forename: W S
authors.initials: WS
authors.lastname: Law
authors.forename: M Y
authors.initials: MY
authors.lastname: Wong
authors.forename: M
authors.initials: M
authors.lastname: Leung
authors.forename: D
authors.initials: D
authors.lastname: Tsui
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D015331:Cohort Studies; D016001:Confidence Intervals; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology / Q000302:isolation & purification*; D016017:Odds Ratio; D011336:Probability; D012189:Retrospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D012829:Silicosis / Q000175:diagnosis* / Q000453:epidemiology; D012882:Skin Tests; D014374:Tuberculin Test; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000453:epidemiology