Table 2 Sensitivity and specificity of the investigational assay, with treatment history as the reference standard

From: Diagnostic accuracy of a liquid chromatography-tandem mass spectrometry assay in small hair samples for rifampin-resistant tuberculosis drug concentrations in a routine care setting

Drug Sensitivitya Specificityb Drug concentration (ng/mg)
True positives False positives
No. detected/no. taking drugs % (95% CI) No. not detected/no. not taking drugs % (95% CI) Median (IQR) Median (IQR)
Isoniazid 31/33 93.9 (79.8–99.3) 12/20 60 (36.1–80.9) 0.99 (0.32–2.21) 0.33 (0.25–0.46)
Pyrazinamide 54/54 100 (93.3–100) 0/2 0 (0–84.2) 9.84 (4.52–18.54) 0.26 (0.22–0.38)
Ethambutol 45/45 100 (92.1–100) 0/10 0 (0–30.8) 0.92 (0.43–1.53) 0.05 (0.02–0.35)
Levofloxacin 30/30 100 (88.4–100) 2/26 7.7 (0.9–25.1) 26.46 (11.53–48.08) 0.63 (0.32–1.06)
Moxifloxacin 41/41 100 (91.4–100) 0/13 0 (0–26.5) 13.81 (6.23–18.32) 2.04 (0.46–4.91)
Linezolid 22/23 95.6 (78.1–99.9) 26/32 81.3 (64.6–92.8) 9.12 (4.20–17.66) 0.16 (0.14–0.43)
Clofazimine 34/34 100 (89.7–100) 2/22 9.1 (1.1–29.2) 2.98 (1.39–4.59) 0.20 (0.05–0.67)
Bedaquiline 27/27 100 (87.2–100) 7/28 25 (10.7–44.9) 0.90 (0.71–1.46) 0.21 (0.10–0.35)
Pretomanid 1/1 100 (2.5–100) 55/56 98.2 (90.4–100) -c
Ethionamide 20/34 58.5 (40.7–99.9) 20/20 100 (83.2–100)
  1. a For sensitivity, the reference standard was considered ‘positive’ if the drug was taken for at least 14 days during the hair growth window
  2. b For specificity, the reference standard was considered ‘negative’ if the drug is not taken for any days in the previous 124 days prior to and including the day of hair collection. For BDQ and CFZ, the reference standard was ‘negative’ if there was no known history of past use of the drug at any time
  3. c Not enough data points for comparison