Table 3.
Diagnostic performance of fluorescence microscopy using different light and/or power sources compared to mycobacterial culture as the reference standard
| Mercury vapour lamp |
LED, mains electricity |
LED, battery-operated |
||||
|---|---|---|---|---|---|---|
| Diagnostic performance | n/N | % (95%CI) | n/N | % (95%CI) | n/N | % (95%CI) |
| Sensitivity* | ||||||
| ≥1+ positive | 43.5/84 | 51.8 (40.2–60.1) | 40.5/84 | 48.2 (38.4–59.3) | 14/28 | 50.0 (32.6–67.4) |
| ≥2+ positive | 29/84 | 34.5 (25.2–45.2) | 26.5/84 | 31.5 (23.1–42.7) | 12/28 | 42.9 (26.5–60.9) |
| Specificity* | ||||||
| ≥1+ positive | 29/37 | 78.4 (62.8–88.6) | 29/37 | 78.4 (62.8–88.6) | 13/15 | 86.7 (62.1–96.3) |
| ≥2+ positive | 33/37 | 89.2 (75.3–95.7) | 31.5/37 | 85.1 (68.7–92.4) | 15/15 | 100.0 (79.6–100) |
| PPV, %† | ||||||
| ≥1+ positive | 66.2 | 64.6 | 75.4 | |||
| ≥2+ positive | 72.3 | 63.5 | 100 | |||
| NPV, %† | ||||||
| ≥1+ positive | 66.5 | 64.9 | 67.9 | |||
| ≥2+ positive | 62.5 | 60.3 | 68.1 | |||
| κ value inter-observer variation | ||||||
| ≥1+ positive | 0.5 (0.37–0.63) | 0.5 (0.37–0.63) | NA | |||
| ≥2+ positive | 0.7 (0.59–0.82) | 0.6 (0.49–0.75) | NA | |||
*
Average for the two readers combined.
†
Calculated by using Bayes’ theorem; prior prevalence has been estimated at 45% from a previous prospective study.15
LED = light-emitting diode; CI = confidence interval; PPV = positive predictive value; NPV = negative predictive value; NA = not applicable; performed on a subgroup and read by a single reader.