TABLE 2.
Test characteristics of rectal swabs with or without visible pigment using stool specimen test results as the reference standard on either a GVP or a Luminex GPPa
| Characteristic and pigment visible on swab | No. of rectal swab specimens |
Testing characteristics of rectal swab for enteropathogen detectionb |
||||||
|---|---|---|---|---|---|---|---|---|
| Stool test positive |
Stool test negative |
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| Swab test positive | Swab test negative | Swab test positive | Swab test negative | Sensitivity (% [95% CI]) | Specificity (% [95% CI]) | PPV (% [95% CI]) | NPV (% [95% CI]) | |
| Overall | ||||||||
| Yes | 682 | 58 | 15 | 246 | 92.2 (90.0, 94.0) | 94.3 (90.5, 96.6) | 97.9 (96.4, 98.8) | 80.9 (76.0, 85.1) |
| No | 523 | 102 | 19 | 196 | 83.7 (80.5, 86.4) | 91.2 (86.3, 94.5) | 96.5 (94.5, 97.8) | 65.8 (60.0, 71.1) |
| Difference | 8.5 (4.9, 12.1) | 3.1 (−1.9, 8.5) | 1.4 (−0.6, 3.6) | 15.2 (7.9, 22.2) | ||||
| Diarrhea present at enrollment | ||||||||
| Yes | 522 | 19 | 9 | 137 | 96.5 (94.5, 97.8) | 93.8 (88.3, 96.7) | 98.3 (96.7, 99.2) | 87.8 (81.4, 92.3) |
| No | 406 | 45 | 14 | 100 | 90.0 (86.8, 92.6) | 87.7 (79.9, 92.9) | 96.7 (94.3, 98.1) | 69.0 (60.7, 76.2) |
| Difference | 6.5 (3.2, 10.0) | 6.1 (−1.5, 14.5) | 1.6 (−0.5, 4.1) | 18.9 (9.2, 28.3) | ||||
| Isolated vomiting at enrollment | ||||||||
| Yes | 160 | 39 | 6 | 108 | 80.4 (74.1, 85.5) | 94.7 (88.4, 97.8) | 96.4 (92.0, 98.5) | 73.5 (65.4, 80.3) |
| No | 115 | 57 | 5 | 95 | 66.9 (59.2, 73.7) | 95.0 (88.2, 98.1) | 95.8 (90.1, 98.5) | 62.5 (54.3, 70.1) |
| Difference | 13.5 (4.2, 22.7) | −0.3 (−7.3, 7.2) | 0.6 (−4.6, 6.7) | 11.0 (−0.09, 21.6) | ||||
| Swab collected in ED | ||||||||
| Yes | 468 | 55 | 11 | 197 | 89.5 (86.5, 91.9) | 94.7 (90.5, 97.2) | 97.7 (95.8, 98.8) | 78.2 (72.5, 83.1) |
| No | 429 | 93 | 18 | 175 | 82.2 (78.6, 85.3) | 90.7 (85.4, 94.2) | 96.0 (93.6, 97.5) | 65.3 (59.2, 70.9) |
| Difference | 7.3 (2.9, 11.7) | 4.0 (−1.5, 9.8) | 1.7 (−0.7, 4.4) | 12.9 (4.9, 20.6) | ||||
| Swab collected at home | ||||||||
| Yes | 214 | 3 | 4 | 49 | 98.6 (95.7, 99.6) | 92.5 (80.9, 97.6) | 98.2 (95.1, 99.4) | 94.2 (83.1, 98.5) |
| No | 94 | 9 | 1 | 21 | 91.3 (83.6, 95.7) | 95.5 (75.1, 99.8) | 99.0 (93.5, 99.9) | 70.0 (50.4, 84.6) |
| Difference | 7.4 (2.1, 15.1) | −3.0 (−15.3, 18.0) | −0.8 (−4.0, 4.9) | 24.2 (5.9, 44.3) | ||||
a
Analyses were stratified by clinical features. PPV, positive predicted value; NPV, negative predictive value; ED, emergency department.
b
The calculation of sensitivity, specificity, PPV, and NPV was done using test results based on stool specimens as the reference standard (see Table S3 in the supplemental material).