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1.  T-cell assay conversions and reversions among household contacts of tuberculosis patients in rural India 
Interferon-gamma assays (IGRAs) are alternatives to the tuberculin skin test (TST), but IGRA conversions and reversions are not well understood. In a pilot study, we determined conversions and reversions using QuantiFERON-TB Gold In-Tube® (QFT) among household contacts of TB cases, and evaluated the effect of using various definitions and criteria for conversions.
In a cohort of 250 contacts in India, 46% were TST-positive at baseline and 54% were QFT-positive. We re-tested this cohort after 12 months. Conversion rates were estimated using several definitions.
Of the 250 contacts, 205 (82%) underwent re peat testing. Among 85 contacts with baseline TST-negative/QFT-negative results, TST conversion rates ranged between 7.5% and 13.8%, and QFT conversion rates ranged between 11.8% and 21.2%, depending on the definitions used. Among 109 contacts who were QFT-positive at baseline, seven (6.4%) had QFT reversions. QFT reversions were most likely when the baseline TST was negative and QFT results were just above the diagnostic cut-off.
QFT conversions and reversions occurred among contacts of TB cases. Conversion rates seemed to vary, depending on the test and definitions used for conversions. These findings need to be verified in larger studies in various settings.
PMCID: PMC2951989  PMID: 19105884 CAMSID: cams238
tuberculosis; interferon-gamma assay; tuberculin skin test; QuantiFERON-TB Gold; contacts; serial testing
2.  Effect of Age and Vaccination With a Pneumococcal Conjugate Vaccine on the Density of Pneumococcal Nasopharyngeal Carriage 
This study evaluated the impact of age and pneumococcal vaccination on the density of pneumococcal nasopharyngeal carriage. Among colonized individuals, density decreased with increasing age. Time-trends analysis revealed that pneumococcal vaccination appeared to lower the density of nasopharyngeal carriage.
Background. This study evaluated the impact of age and pneumococcal vaccination on the density of pneumococcal nasopharyngeal carriage.
Methods. A cluster-randomized trial was conducted in rural Gambia. In 11 villages (the vaccine group), all residents received 7-valent pneumococcal conjugate vaccine (PCV-7), while in another 10 villages (the control group), only children <30 months old or born during the study period received PCV-7. Cross-sectional surveys (CSSs) were conducted to collect nasopharyngeal swabs before vaccination (baseline CSS) and 4, 12, and 22 months after vaccination. Pneumococcal density was defined using a semiquantitative classification (range, 1–4) among colonized individuals. An age-trend analysis of density was conducted using data from the baseline CSS. Mean pneumococcal density was compared in CSSs conducted before and after vaccination.
Results. Mean bacterial density among colonized individuals in the baseline CSS was 2.57 for vaccine-type (VT) and non–vaccine-type (NVT) pneumococci; it decreased with age (P < .001 for VT and NVT). There was a decrease in the density of VT carriage following vaccination in individuals older than 5 years (from 2.44 to 1.88; P = .001) and in younger individuals (from 2.57 to 2.11; P = .070) in the vaccinated villages. Similar decreases in density were observed with NVT within vaccinated and control villages. No significant differences were found between vaccinated and control villages in the postvaccination comparisons for either VT or NVT.
Conclusions. A high density of carriage among young subjects might partly explain why children are more efficient than adults in pneumococcal transmission. PCV-7 vaccination lowered the density of VT and of NVT pneumococcal carriage in the before-after vaccination analysis.
Clinical Trials Registration. ISRCTN51695599.
PMCID: PMC3423933  PMID: 22700830

Results 1-2 (2)