Table 4.
Sensitivity, specificity, PPV and NPV of LM for detecting Plasmodium falciparum against nested PCR as a reference method
| PCR + ve | PCR + ve | PCR−ve | PCR−ve | Sensitivity | Specificity | PPV | NPV | % Agreement* | |
|---|---|---|---|---|---|---|---|---|---|
| LM + ve | LM−ve | LM−ve | LM + ve | % (95 % CI) | % (95 % CI) | % (95 % CI) | % (95 % CI) | (Kc) | |
| Overall | 47 | 78 | 82 | 2a | 37.6 (29.6–46.3) | 97.6 (91.7–99.7) | 95.9 (86.3–98.9) | 51.3 (43.2–59.2) | 61.7 (0.307) |
| Age (years) (n = 209) | |||||||||
| ≥10 | 41 | 65 | 71 | 2 | 38.7 (30.0–48.2) | 97.3 (90.5–99.7) | 95.3 (84.5–98.7) | 52.2 (43.5–60.8) | 62.6 (0.329) |
| <10 | 6 | 13 | 11 | 0 | 31.6 (12.6–56.6) | 100 (71.5–100) | 100 (54.1–100) | 45.8 (25.6–67.2) | 56.7 (0.253) |
| Fever 48 h prior to study (n = 209) | |||||||||
| Yes | 40 | 3 | 2 | 2 | 93.0 (81.4–97.6) | 50.0 (6.8–93.2) | 95.2 (84.2–98.7) | 40.0 (5.3–85.3) | 89.4 (0.386) |
| No | 7 | 75 | 80 | 0 | 8.5 (3.5–16.8) | 100 (95.5–100) | 100 (59.0–100) | 51.6 (43.5–59.7) | 53.7 (0.084) |
| History of anti-malarial drug intake 1 week prior to the survey (n = 208) | |||||||||
| Yes | 19 | 37 | 30 | 0 | 33.9 (22.9–47.0 | 100 (88.4–100) | 100 (83.2–100) | 44.8 (33.5–56.6) | 57.0 (0.264) |
| No | 28 | 40 | 52 | 2 | 41.2 (30.3–53.0) | 96.3 (87.5–99) | 93.3 (78.7–98.2) | 56.5 (46.3–66.2) | 75.6 (0.349) |
CI confidence interval, PCR polymerase chain reaction, LM light microscopy, PPV positive predictive value, NPV negative predictive value, Kc Cohen’s kappa coefficient; % agreement was calculated by summation of the number of positives and negatives by both LM and PCR divided by the total number of cases
* The agreement between LM and PCR was significant in all categories with p < 0.05
aParasite densities of these two cases were 80 parasites and 400 parasites/µL