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TST positivity in household contacts of tuberculosis patients: a case-contact study in Malawi.

Hector, Jonas, Anderson, Suzanne T, Banda, Gertrude, Kamdolozi, Mercy, Jefferys, Laura, Shani, Doris, Garton, Natalie J, Mwale, Agnes, Jobe, Annie, Davies, Geraint R and Sloan, Derek J (2017) 'TST positivity in household contacts of tuberculosis patients: a case-contact study in Malawi.'. BMC Infectious Diseases, Vol 17, Issue 1, e259.

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Abstract

Screening household contacts of active tuberculosis (TB) patients is recommended for TB control. Due to resource constraints this rarely occurs in lower income countries. Demographic and clinical features of index cases may influence the likelihood of onwards TB transmission. It has also been proposed that accumulation of intracellular lipid bodies within M. tuberculosis cells may also enhance bacterial transmissibility. This study explored whether clinical and bacteriological observations recorded at baseline in TB cases in Malawi could help identify those with the highest risk of onwards transmission, to prioritise contact tracing. In this case-contact study, data on clinical presentation, sputum bacterial load and the percentage of lipid body positive acid-fast bacilli (%LB + AFB) on sputum smears were recorded in adults with sputum smear and culture positive pulmonary TB before initiation of therapy. The Tuberculin Skin Test (TST) was used to detect infection with M. tuberculosis amongst household contacts under the age of 15 years. TST positivity of the child contacts was related to characteristics of the index case. Thirty four index cases brought 56 contacts (median: 1, range: 1-4 contacts each). 37 (66%) of contacts had a positive TST. Cavities or a high percentage of lung affected on index patient CXRs were associated with TST positivity. Multivariate analysis of non-radiological factors showed that male sex, HIV-negative status and raised peripheral blood white blood count (WBC) in index patients were also independent risk factors of TST positivity. Lower %LB + AFB counts were associated with TST positivity on univariate analysis only. TST positivity is common amongst household contacts of sputum smear positive adult TB patients in Malawi. Contact tracing in this high risk population could be guided by prioritising index cases with CXR cavities and extensive radiological disease or, in the absence of CXRs, those who are HIV-negative with a raised WBC.

Item Type: Article
Subjects: WA Public Health > WA 30 Socioeconomic factors in public health (General)
WA Public Health > Health Problems of Special Population Groups > WA 395 Health in developing countries
WF Respiratory System > Tuberculosis > WF 200 Tuberculosis (General)
WF Respiratory System > Tuberculosis > WF 220 Diagnosis. Prognosis
Faculty: Department: Clinical Sciences & International Health > Clinical Sciences Department
Digital Object Identifer (DOI): https://doi.org/10.1186/s12879-017-2348-2
SWORD Depositor: JISC Pubrouter
Depositing User: JISC Pubrouter
Date Deposited: 04 May 2017 16:45
Last Modified: 06 Feb 2018 13:14
URI: http://archive.lstmed.ac.uk/id/eprint/7038

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