TST positivity in household contacts of tuberculosis patients: a case-contact study in Malawi
Abstract Background 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...
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| Format: | Article |
| Language: | English |
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BMC
2017-04-01
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| Series: | BMC Infectious Diseases |
| Subjects: | |
| Online Access: | http://link.springer.com/article/10.1186/s12879-017-2348-2 |
| _version_ | 1818328386356903936 |
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| author | Jonas Hector Suzanne T. Anderson Gertrude Banda Mercy Kamdolozi Laura F. Jefferys Doris Shani Natalie J. Garton Agnes Mwale Annie Jobe Geraint R. Davies Derek J Sloan |
| author_facet | Jonas Hector Suzanne T. Anderson Gertrude Banda Mercy Kamdolozi Laura F. Jefferys Doris Shani Natalie J. Garton Agnes Mwale Annie Jobe Geraint R. Davies Derek J Sloan |
| author_sort | Jonas Hector |
| collection | DOAJ |
| description | Abstract Background 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. Methods 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. Results 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. Conclusion 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. |
| first_indexed | 2024-12-13T12:31:20Z |
| format | Article |
| id | doaj.art-3e2e5b6a1a83455b96917503ea55a1a3 |
| institution | Directory Open Access Journal |
| issn | 1471-2334 |
| language | English |
| last_indexed | 2024-12-13T12:31:20Z |
| publishDate | 2017-04-01 |
| publisher | BMC |
| record_format | Article |
| series | BMC Infectious Diseases |
| spelling | doaj.art-3e2e5b6a1a83455b96917503ea55a1a32022-12-21T23:46:01ZengBMCBMC Infectious Diseases1471-23342017-04-011711710.1186/s12879-017-2348-2TST positivity in household contacts of tuberculosis patients: a case-contact study in MalawiJonas Hector0Suzanne T. Anderson1Gertrude Banda2Mercy Kamdolozi3Laura F. Jefferys4Doris Shani5Natalie J. Garton6Agnes Mwale7Annie Jobe8Geraint R. Davies9Derek J Sloan10LSTM, Liverpool School of Tropical MedicineMalawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, University of MalawiMalawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, University of MalawiDepartment of Microbiology, College of Medicine, University of MalawiLSTM, Liverpool School of Tropical MedicineDepartment of Microbiology, College of Medicine, University of MalawiDepartment of Infection, Immunity and Inflammation, University of LeicesterMalawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, University of MalawiMalawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, University of MalawiInstitute of Infection and Global Health, University of LiverpoolMalawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, University of MalawiAbstract Background 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. Methods 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. Results 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. Conclusion 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.http://link.springer.com/article/10.1186/s12879-017-2348-2TuberculosisHIV statusContact screeningTuberculosis skin testWhite blood cell countMalawi |
| spellingShingle | Jonas Hector Suzanne T. Anderson Gertrude Banda Mercy Kamdolozi Laura F. Jefferys Doris Shani Natalie J. Garton Agnes Mwale Annie Jobe Geraint R. Davies Derek J Sloan TST positivity in household contacts of tuberculosis patients: a case-contact study in Malawi BMC Infectious Diseases Tuberculosis HIV status Contact screening Tuberculosis skin test White blood cell count Malawi |
| title | TST positivity in household contacts of tuberculosis patients: a case-contact study in Malawi |
| title_full | TST positivity in household contacts of tuberculosis patients: a case-contact study in Malawi |
| title_fullStr | TST positivity in household contacts of tuberculosis patients: a case-contact study in Malawi |
| title_full_unstemmed | TST positivity in household contacts of tuberculosis patients: a case-contact study in Malawi |
| title_short | TST positivity in household contacts of tuberculosis patients: a case-contact study in Malawi |
| title_sort | tst positivity in household contacts of tuberculosis patients a case contact study in malawi |
| topic | Tuberculosis HIV status Contact screening Tuberculosis skin test White blood cell count Malawi |
| url | http://link.springer.com/article/10.1186/s12879-017-2348-2 |
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