Comparison of the QuantiFERON®-TB Gold assay and tuberculin skin test to detect latent tuberculosis infection among target groups in Trinidad & Tobago.

OBJECTIVE: To compare the QuantiFERON®-TB Gold (QFT-G) assay and tuberculin skin test (TST) in screening/diagnosis of latent tuberculosis infection (LTBI) among individuals in Trinidad & Tobago at high risk for TB. METHODS: A total of 560 individuals (TB patient contacts, HIV patients, health care workers, prison inmates, and TB patients [controls]) were recruited for the study. Blood was drawn and processed using the QFT-G assay, followed by immediate administration of TST solution on subjects' forearm. Data were analyzed with Epi InfoTM 3.5.1 software. Results were compared across the target groups using the chi-square test (P < 0.05). RESULTS: The QFT-G assay detected LTBI in 51% of the subjects (with most positive results occurring among the control group) whereas the TST detected it in 39.4% (P = 0.001). Overall, the QFT-G assay detected LTBI more frequently than the TST among all subjects except the control group, where detection favored the TST. The QFT-G assay produced indeterminate and nonreactive results in some HIV patients but required less turnaround time than the TST (23.3 h versus 70.2 h; P < 0.0001). The TST cost less per subject than the QFT-G assay (US $3.70 versus US $18.60; P = 0.0008). CONCLUSIONS: The QFT-G assay cost more but had a higher detection rate among most target groups and required less turnaround time than the TST. However, its sensitivity was lower among immunocompromised subjects. Therefore, the QFT-G assay should be used with caution for LBTI screening/diagnosis in resource-poor, high-HIV prevalence settings such as Trinidad & Tobago.

Comparison of the QuantiFERON®-TB Gold assay and tuberculin skin test to detect latent tuberculosis infection among target groups in Trinidad & Tobago / Comparación entre la prueba QuantiFERON®-TB Gold y la prueba cutánea de la tuberculina para detectar la infección tuberculosa latente en grupos destinatarios en Trinidad y Tabago

OBJECTIVE: To compare the QuantiFERON®-TB Gold (QFT-G) assay and tuberculin skin test (TST) in screening/diagnosis of latent tuberculosis infection (LTBI) among individuals in Trinidad & Tobago at high risk for TB. METHODS: A total of 560 individuals (TB patient contacts, HIV patients, health care workers, prison inmates, and TB patients [controls]) were recruited for the study. Blood was drawn and processed using the QFT-G assay, followed by immediate administration of TST solution on subjects' forearm. Data were analyzed with Epi InfoTM 3.5.1 software. Results were compared across the target groups using the chi-square test (P < 0.05). RESULTS: The QFT-G assay detected LTBI in 51 percent of the subjects (with most positive results occurring among the control group) whereas the TST detected it in 39.4 percent (P = 0.001). Overall, the QFT-G assay detected LTBI more frequently than the TST among all subjects except the control group, where detection favored the TST. The QFT-G assay produced indeterminate and nonreactive results in some HIV patients but required less turnaround time than the TST (23.3 h versus 70.2 h; P < 0.0001). The TST cost less per subject than the QFT-G assay (US $3.70 versus US $18.60; P = 0.0008). CONCLUSIONS: The QFT-G assay cost more but had a higher detection rate among most target groups and required less turnaround time than the TST. However, its sensitivity was lower among immunocompromised subjects. Therefore, the QFT-G assay should be used with caution for LBTI screening/diagnosis in resource-poor, high-HIV prevalence settings such as Trinidad & Tobago.

OBJETIVO: Comparar la prueba QuantiFERON®-TB Gold (QFT-G) con la prueba cutánea de la tuberculina (PPD) para el tamizaje y diagnóstico de la infección tuberculosa latente (ITBL) en personas con alto riesgo de tuberculosis en Trinidad y Tabago. MÉTODOS: Para el estudio, se reclutó un total de 560 individuos (personas en contacto con pacientes de tuberculosis, pacientes con VIH, trabajadores de la salud, presidiarios y pacientes de tuberculosis [grupo testigo]). Las muestras de sangre se extrajeron y procesaron utilizando la prueba QFT-G, seguida de la aplicación inmediata de la solución de PPD en el antebrazo de las personas. Los datos se analizaron con el software Epi InfoTM 3.5.1. Los resultados obtenidos en los grupos destinatarios se compararon utilizando la prueba de la ji al cuadrado (P < 0,05). RESULTADOS: La prueba QFT-G detectó la infección tuberculosa latente en 51 por ciento de los individuos (la mayoría de los resultados positivos se presentaron en el grupo testigo) mientras que la prueba PPD la detectó en 39,4 por ciento (P = 0,001). En términos generales, la prueba QFT-G detectó la infección tuberculosa latente con mayor frecuencia que la PPD en todos los individuos, excepto en aquellos del grupo testigo, donde el índice de detección favoreció a la PPD. La prueba QFT-G produjo resultados indeterminados y no reactivos en algunos pacientes con VIH, pero requirió menos tiempo de respuesta que la PPD (23,3 h contra 70,2 h; P < 0.0001). La prueba PPD tuvo un costo menor por individuo que la QFT-G (US$3,70 en comparación con US$18,60; P = 0.0008). CONCLUSIONES: La prueba QFT-G tuvo un costo más elevado, pero la tasa de detección fue más alta en la mayoría de los grupos destinatarios y el tiempo de respuesta fue más rápido en comparación con la PPD. Sin embargo, la sensibilidad de la prueba QFT-G fue inferior entre los individuos inmunodeficientes. Por consiguiente, se deben tomar las precauciones necesarias para utilizar la prueba QFT-G en el tamizaje y diagnóstico de ITBL en entornos de escasos recursos y alta prevalencia de VIH como Trinidad y Tabago.

Phylogeographical and molecular characterization of an emerging Mycobacterium tuberculosis clone in Trinidad and Tobago.

We report on a fine molecular and phylogenetical characterization of circulating Mycobacterium tuberculosis strains isolated from patients during a 1-year period in Trinidad and Tobago (T&T). The spoligotyping data coupled to minisatellite typing and available epidemiological data showed that a single major clone of "evolutionary modern" tubercle bacilli (SIT566) was responsible for more than half of the tuberculosis (TB) cases. It preferentially infected younger age groups (mean 39.1 years versus 47.7 years for other genotypes, p<0.0005), and was overrepresented in Port-of-Spain (1 out of 3 patients). A comparison of genotyping results to data gathered for 6 Caribbean countries (n=2653 clinical isolates) showed that the overall lineage distribution in T&T was completely different from its neighbors, e.g., T&T was the only country harboring a unique sublineage of the Latin American & Mediterranean (LAM) family, designated LAM-10CAM with phylogeographical specificity for Cameroon and neighboring countries in West Africa; interestingly 3/4 of the patients within this group in T&T were African descendants. Similarly, strains belonging to East African Indian (EAI) lineage with phylogeographical specificity for the Indian subcontinent, were found in T&T (13% of all strains), but were absent among the neighboring countries. Although the predominant SIT566 was not yet detected elsewhere in the Caribbean, available information underlined that this genotype was already present in the United States as imported cases of disease among T&T-born patients. Characterization of SIT566 strains using 12-, 15- and 24-loci MIRU typing, and comparison of results to international databases showed that these isolates were characterized by a common 12-loci MIRU pattern 224315153324 corresponding to MIRU International Type-MIT633 in 21/25 strains tested, as well as its 4 variants; an orphan pattern , MIT27-, MIT117-, and MIT1158-. Extended 24-loci MIRU typing led to a predominant pattern 224315153324323483334323 in a total of 16/21 MIT633 isolates, as well as identification of 3 supplemental patterns. Comparison of 24-loci MIRU data with the international database MIRU-VNTRplus showed the unique nature of the patterns obtained in T&T. Further analysis using the Levenshtein algorithm showed that the first 2 closest matches with the SIT566/MIT633 clone belonged to the X lineage strains in MIRU-VNTRplus. This observation corroborates our preliminary spoligotyping-based analysis using minimum spanning and neighbor-joining trees, which suggested a phylogenetical relatedness of the SIT566 clone with SIT119, which represents X1 lineage prototype in SpolDB4 database. We hypothesize that the predominant SIT566 clone might have evolved from a pool of X lineage M. tuberculosis strains with phylogeographical affinity for Anglo-Saxon descendants.

First insight into Mycobacterium tuberculosis epidemiology and genetic diversity in Trinidad and Tobago.

This report is based on a 1-year recruitment of all of the culture-positive Mycobacterium tuberculosis cases in Trinidad and Tobago (n = 132). The study population was characterized by a high male-to-female sex ratio of 4 and a human immunodeficiency virus-tuberculosis (TB) coinfection rate of 30 per cent. It mainly occurred among African descendants, who represent 37.5 per cent of the total population but 69.7 per cent of all TB cases (P < 0.001). Spoligotyping resulted in 25 different patterns and 12 clusters (2 to 74 strains per cluster), with the predominance of a highly conserved spoligotype international type clone, SIT566.

First insight into Mycobacterium tuberculosis epidemiology and genetic diversity in Trinidad and Tobago.

This report is based on a 1-year recruitment of all of the culture-positive Mycobacterium tuberculosis cases in Trinidad and Tobago (n = 132). The study population was characterized by a high male-to-female sex ratio of 4 and a human immunodeficiency virus-tuberculosis (TB) coinfection rate of 30%. It mainly occurred among African descendants, who represent 37.5% of the total population but 69.7% of all TB cases (P < 0.001). Spoligotyping resulted in 25 different patterns and 12 clusters (2 to 74 strains per cluster), with the predominance of a highly conserved spoligotype international type clone, SIT566.