Spot sputum samples are at least as good as early morning samples for identifying Mycobacterium tuberculosis

Table 2 Odds ratios of paired EMS and spot sputum smear grading and culture time-to-detection for predicting an unfavourable outcome (logistic regression)

Baseline predictor variable		EMS			Spot
Baseline predictor variable		OR	95% CI	P value	OR	95%	P value
Baseline smear grading*	ZN Neg	0.63	0.18–2.11	0.45	–	–	–
	ZN 1+	0.50	0.17–1.42	0.19	0.22	0.08–0.63	0.004
	ZN 2+	0.38	0.17–0.87	0.02	0.82	0.48–1.39	0.46
	ZN 3+	0.56	0.33–0.95	0.03	0.68	0.43–1.07	0.09
	ZN 4+	Reference			Reference
Log₁₀ LJ TTD		0.61	0.26–1.45	0.26	0.73	0.29–1.87	0.51
Log₁₀ MGIT TTP		0.38	0.13–1.10	0.07	0.29	0.08–0.99	0.05

*Unfavourable outcome is associated with increasing ZN smear for both EMS (P = 0.008) and spot (P = 0.002), non-parametric test for trend
CI confidence interval, EMS early morning sputum sample, LJ Lowenstein–Jensen, MGIT mycobacteria growth indicator tube, OR odds ratio, TTD time-to-detection, TTP time-to-positivity, ZN Ziehl–Neelsen

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