title: Serial QuantiFERON-TB Gold In-Tube assay and tuberculin skin test to diagnose latent tuberculosis in household Mexican contacts: conversion and reversion rates and associated factors using conventional and borderline zone definitions.
abstract: A cohort of 123 adult contacts was followed for 18-24 months (86 completed the follow-up) to compare conversion and reversion rates based on two serial measures of QuantiFERON (QFT) and tuberculin skin test (TST) (PPD from TUBERSOL, Aventis Pasteur, Canada) for diagnosing latent tuberculosis (TB) in household contacts of TB patients using conventional (C) and borderline zone (BZ) definitions. Questionnaires were used to obtain information regarding TB exposure, TB risk factors and socio-demographic data. QFT (IU/mL) conversion was defined as <0.35 to ≥0.35 (C) or <0.35 to >0.70 (BZ) and reversion was defined as ≥0.35 to <0.35 (C) or ≥0.35 to <0.20 (BZ); TST (mm) conversion was defined as <5 to ≥5 (C) or <5 to >10 (BZ) and reversion was defined as ≥5 to <5 (C). The QFT conversion and reversion rates were 10.5% and 7% with C and 8.1% and 4.7% with the BZ definitions, respectively. The TST rates were higher compared with QFT, especially with the C definitions (conversion 23.3%, reversion 9.3%). The QFT conversion and reversion rates were higher for TST ≥5; for TST, both rates were lower for QFT <0.35. No risk factors were associated with the probability of converting or reverting. The inconsistency and apparent randomness of serial testing is confusing and adds to the limitations of these tests and definitions to follow-up close TB contacts.
authors.affiliation: Department of Public Health Sciences, Karolinska Institute, Stockholm, Sweden.
authors.forename: Joel
authors.initials: J
authors.lastname: Monárrez-Espino
authors.affiliation: Medical Research Unit Zacatecas, Mexican Institute of Social Security, Zacatecas, Mexico.
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Enciso-Moreno
authors.affiliation: Department of Public Health Sciences, Karolinska Institute, Stockholm, Sweden.
authors.forename: Lucie
authors.initials: L
authors.lastname: Laflamme
authors.affiliation: Medical Research Unit Zacatecas, Mexican Institute of Social Security, Zacatecas, Mexico.
authors.forename: Carmen J
authors.initials: CJ
authors.lastname: Serrano
mesh_terms: D000328:Adult; D016358:Contact Tracing; D018450:Disease Progression; D004781:Environmental Exposure; D005069:Evaluation Studies as Topic; D005191:Family Characteristics; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D055985:Latent Tuberculosis / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology / Q000635:transmission*; D008297:Male; D008800:Mexico / Q000453:epidemiology; D008875:Middle Aged; D012307:Risk Factors; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D014374:Tuberculin Test / Q000379:methods*