Tuberculosis in the Torres Strait: the lady doth test too much

Foster, J'Belle, Marais, Ben, Martin, Rotona L., Peniyamina, Dunstan, Mendez, Diana, Warner, Jeffrey, and McBryde, Emma (2021) Tuberculosis in the Torres Strait: the lady doth test too much. Rural and Remote Health, 21 (1). 6317.

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Introduction: Smear-positive pulmonary tuberculosis (PTB) requires rapid diagnosis and treatment to prevent ongoing transmission. Collection of two sputum specimens is considered the minimum requirement for the diagnosis of PTB but current guidelines in the Torres Strait Islands, Australia, recommend three sputum specimens; this frequently delays treatment initiation.

Methods: A retrospective study was performed to ascertain the diagnostic yield of sputum specimens collected in the Torres Strait Islands. The study assessed demographics and characteristics of all PTB cases diagnosed between 2000 and 2018, and assessed the diagnostic yield in 143 patients from whom at least three sputum specimens had been collected prior to treatment commencement. Incremental and cumulative yield was calculated for each sputum specimen. Data were further analysed using binary logistic regression to examine the association between selected characteristics and a smear-positive acid-fast bacilli (AFB) result.

Results: Overall, AFB was detected from the first or second sputum specimen in 97 of 101 PTB cases that were sputum smear positive. A smear-positive result was more common (odds ratio 2.84, 95% confidence interval 1.08–7.46) for Papua New Guinea nationals compared to Australian born patients. Of the 429 samples collected, 76 (18%) were of poor quality and the association between poor quality specimens and smear-negative results was significant (p<0.01). Among sputum smear-negative cases, 5/42= (12%) had three consecutive poor quality specimens. The most common collection modality in adults was voluntary expectoration; done in 391/429 (91%) of all specimens collected. Alternative specimen collection methods were mainly used in children; induced sputum 1/429 (0.2%), gastric aspirate 26/429 (6%) and nasopharyngeal aspirate 7/429 (1.6%). Errors with labelling, packaging and transportation occurred in 44 specimens from 15 patients.

Conclusion: Two good quality specimens ensure adequate diagnostic yield for PTB and a third specimen should only be collected from patients with two negative specimens who have persistent symptoms. Ideally, decentralised Xpert Ultra® should be the frontline diagnostic test in remote settings, especially in settings like the Torres Strait Islands with high rates of drugresistant TB.

Item ID: 70756
Item Type: Article (Research - C1)
ISSN: 1445-6354
Keywords: diagnostic yield, sputum smear positive, Torres Strait., tuberculosis
Copyright Information: This work is licensed under a Creative Commons Attribution 4.0 International Licence
Date Deposited: 22 Mar 2022 23:49
FoR Codes: 49 MATHEMATICAL SCIENCES > 4901 Applied mathematics > 490102 Biological mathematics @ 30%
42 HEALTH SCIENCES > 4202 Epidemiology > 420205 Epidemiological modelling @ 70%
SEO Codes: 20 HEALTH > 2004 Public health (excl. specific population health) > 200404 Disease distribution and transmission (incl. surveillance and response) @ 80%
20 HEALTH > 2002 Evaluation of health and support services > 200205 Health policy evaluation @ 20%
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