Clinical and Imaging Characteristics of Smear Negative Pulmonary Tuberculosis Patients: A Comparative Study

Table 5

Diagnostic accuracy of AFS smear microscopy and GeneXpert MTB/RTF assay among SNPTB and SPPTB patients, Addis Ababa, Ethiopia, 2021.

Accuracy of AFS vs. GeneXpert compared to the gold standard detecting MTBC among PTB patients
GeneXpert (pooled)	LJ culture (gold standard)
	LJ culture positive	LJ culture negative	Total	AFS (pooled)	LJ culture positive	LJ culture negative	Total
Positive	30	19	49	Positive	38	2	40
Negative	12	48	60	Negative	29	40	69
Total	42	67	109	Total	67	42	109
Accuracy parameters
	(95% conf. inter.)				(95% conf. inter.)
Sensitivity	71.64%	63.18%	80.10%	Sensitivity	56.72%	47.41%	66.02%
Specificity	71.43%	62.95%	79.91%	Specificity	95.24%	91.24%	99.24%
PPV	80.00%	72.49%	87.51%	PPV	95.00%	90.91%	99.09%
NPV	61.22%	52.08%	70.37%	NPV	57.97%	48.70%	67.24%
Prevalence	61.47%	52.33%	70.60%	Prevalence	61.47%	52.33%	70.60%
Accuracy of GeneXpert detecting MTBC among SPPTB patients vs. among SNPTB patients
GeneXpert	SPPTB				SNPTB
	LJ culture positive	LJ culture negative	Total		LJ culture positive	LJ culture negative	Total
Positive	37	2	39	Positive	11	10	21
Negative	1	0	1	Negative	18	30	48
Total	38	2	40	Total	29	40	69
Accuracy parameters
(95% conf. inter.)				(95% conf. inter.)
Sensitivity	97.37%	92.41%	102.33%	Sensitivity	37.93%	26.48%	49.38%
Specificity	0.00%	0.00%	0.00%	Specificity	75.00%	64.78%	85.22%
PPV	94.87%	88.04%	101.71%	PPV			64.17%
NPV	0.00%	0.00%	0.00%	NPV	62.50%	51.08%	73.92%
Prevalence	95.00%	88.25%	101.75%	Prevalence	42.03%	30.38%	53.68%

SNPTB: smear negative pulmonary tuberculosis; SPPTB: smear positive pulmonary tuberculosis; PPV: positive predictive value; NPV: negative predictive value.