Accuracy of the InnowaveDX MTB/RIF test for detection of Mycobacterium tuberculosis and rifampicin resistance: a prospective multicentre study

Figures & data

Figure 1. Limit of detection for the reference MTB H37Rv. The limit of detection of tuberculosis detection is shown for TB detection (A) and rifampicin susceptibility (B).

Figure 2. Participant enrolment.

Table 1. Diagnostic performance of the InnowaveDX assay for TB using microbiological reference standard.

Reference	Sensitivity (%, 95%CI)			Specificity (%, 95%CI)	PPV (%, 95% CI)	NPV (%, 95% CI)
	All	Smear positive	Smear negative
Microbiological reference standard^a	563/607 92.7 (90.3–94.6)	336/354 94.9 (91.9–96.9)	227/253 89.7 (85.1–93.0)	277/344 80.5 (75.9–84.5)	563/630 89.3 (86.6–91.6)	277/321 86.3 (81.9–89.8)

^a The microbiological reference standard is defined as patients with at least one sputum sample culture- and/or Xpert-positive for MTB.

PPV: positive predictive value; NPV: negative predictive value; CI: confidential interval; TB: tuberculosis; MTB: Mycobacterium tuberculosis.

Table 2. Diagnostic performance of the InnowaveDX assay for TB using clinical reference standard.

Reference	Sensitivity (%, 95% CI)	Specificity (%, 95% CI)	PPV (%, 95% CI)	NPV (%, 95% CI)
Clinical reference standard^a	624/739 84.4 (81.6–86.9)	206/212 97.2 (93.7–98.8)	624/630 99.0 (97.8–99.6)	206/321 64.2 (58.6–69.4)

^a The clinical reference standard is defined as patients with final diagnosis of pulmonary TB.

PPV: positive predictive value; NPV: negative predictive value; CI: confidential interval.

Figure 3. Venn diagram of overlap in MTB detection using InnowaveDX, Xpert, smear and mycobacterial MGIT culture in sputum sample. Abbreviations: MGIT, mycobacterial growth indicator tube.

Figure 4. Distribution of cases with discordant RIF susceptibility between Xpert and InnowaveDX stratified by bacterial load.

Table 3. Diagnostic accuracy of the InnowaveDX assay for RIF susceptibility against Xpert.

InnowaveDX	Xpert		Total	Sensitivity (%, 95% CI)	Specificity (%, 95% CI)	PPV (%, 95% CI)	NPV (%, 95% CI)
	R	S
R	108	24	132	86.4 (78.8–91.6)	94.1 (91.3–96.1)	81.8 (74.0–87.8)	95.8 (93.2–97.4)
S	17	386	403
Total	125	410	535

RIF: rifampicin; R: resistant; S: susceptible; PPV: positive predictive value; NPV: negative predictive value; CI: confidential interval.