Skip directly to search Skip directly to A to Z list Skip directly to page options Skip directly to site content

Volume 14, Number 7—July 2008

Research

Determinants of Cluster Size in Large, Population-Based Molecular Epidemiology Study of Tuberculosis, Northern Malawi

Judith R. Glynn*Comments to Author , Amelia C. Crampin*†, Hamidou Traore*, Steve Chaguluka†, Donex T. Mwafulirwa†, Saad Alghamdi*, Bagrey M.M. Ngwira†, Malcolm D. Yates‡, Francis D. Drobniewski‡, and Paul E.M. Fine*
Author affiliations: *London School of Hygiene and Tropical Medicine, London, UK; †Karonga Prevention Study, Chilumba, Malawi; ‡Health Protection Agency, London;

Main Article

Table 1

Associations between patient characteristics and cluster size, Mycobacterium tuberculosis, bivariate analysis, Malawi

Characteristic N Cluster size, %
Odds ratio 
(95% CI)* p value
2–4
(n = 186) 5–10
(n = 196) 11–20
(n = 173) >20
(n = 127)
Age, y 0.05
<25 111 27.9 25.2 25.2 21.6 1
25–34 266 24.4 26.3 27.8 21.4 1.1 (0.74–1.7)
35–44 160 26.3 32.5 25.0 16.3 0.87 (0.56–1.3)
>45
145
33.1
31.7
21.4
13.8
0.66 (0.42–1.0)

Sex 0.1
F 386 27.2 30.3 26.9 15.0 1
M
296
26.7
26.7
23.3
23.3
1.2 (0.95–1.6)

HIV status 1.0
Negative 141 26.2 30.5 23.4 19.9 1
Positive
288
26.4
28.1
27.8
17.7
1.0 (0.7–1.4)

Area 0.005
South, near Chilumba 70 38.6 22.9 24.3 14.3 0.51 (0.31–0.84)
Middle, near Nyungwe 89 20.2 22.5 30.3 27.0 1.2 (0.79–1.9)
Around Karonga 119 25.2 34.5 21.9 18.5 0.73 (0.48–1.1)
Karonga central (urban) 209 21.5 25.4 32.5 20.6 1
Kaporo area 84 35.7 34.5 15.5 14.3 0.46 (0.29–1.1)
Far north 57 28.1 40.4 21.1 10.5 0.54 (0.32–0.9)
Outside district
16
26.9
28.9
25.6
18.6
0.41 (0.61–1.1)

Tuberculosis type 0.6
Smear positive 485 26.2 29.5 25.4 19.0 1
Smear negative 145 29.7 24.8 27.6 17.9 0.94 (0.68–1.3)
Extrapulmonary
52
30.8
32.7
19.2
17.3
0.78 (0.47–1.3)

Previous tuberculosis 0.6
No 628 27.4 28.8 25.8 18.0 1
Yes
47
27.7
25.5
21.3
25.5
1.2 (0.68–2.0)

Isoniazid resistance 0.2
No 641 28.1 27.9 25.9 18.1 1
Yes
39
12.8
43.6
15.4
28.2
1.5 (0.84–2.6)

Died† 1.0
No 382 26.7 28.3 25.1 19.9 1
Yes 155 25.8 29.0 26.5 18.7 1.0 (0.72–1.4)

*Odds ratio from ordered logistic regression. This represents the summary relative odds of larger clusters compared with smaller clusters across the 4 groups. Odds ratios >1 imply that the odds of being in a larger cluster are greater than in the baseline group. CI, confidence interval.
†Outcome recorded for 632 patients; those who were lost or transferred while receiving treatment are excluded from this analysis.

Main Article

TOP