TABLE 1.
Different cutoff values selected for the ELISA with their corresponding sensitivities, specificities, PPVs, NPVs, and delta values
| Cutoff (OD) | Sensitivitya at:
|
Specificityb
|
PPVc,d | NPVd,e | Delta
|
||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1-10 Days | 11-20 Days | 21-30 Days | >30 Days | Total | HD (HK) | HD (USA) | Non-SARS (respiratory) | Non-SARS (fever) | Positive | Negative | |||
| 0.25 | 18/31 (58) | 84/120 (70) | 43/57 (75) | 18/19 (95) | 163/227 (71.8) | 383/385 (99.5) | 1,045/1,066 (98.0) | 50/50 (100) | 46/50 (92) | 163/165 (98.8) | 383/447 (85.7) | 0.53 | 2.42 |
| 0.30 | 16/31 (52) | 78/120 (65) | 42/57 (74) | 18/19 (95) | 155/227 (68.3) | 384/385 (99.7) | 1,050/1,066 (98.5) | 50/50 (100) | 48/50 (96) | 155/156 (99.4) | 384/456 (84.2) | 0.40 | 2.61 |
| 0.45 | 15/31 (48) | 65/120 (54) | 40/57 (70) | 16/19 (84) | 136/227 (59.9) | 385/385 (100) | 1,058/1,066 (99.2) | 50/50 (100) | 49/50 (98) | 136/136 (100) | 385/476 (80.8) | 0.10 | 3.03 |
Given as number of positive samples/number of samples tested (percent).
Given as number of negative samples/number of samples tested (percent). HD (HK), 385 serum samples from healthy donors in Hong Kong; HD (USA), 1,066 serum samples from healthy donors purchased from BioClinical Partners Inc. IF titers were not determined for the healthy controls from BioClinical Partners or for the non-SARS disease controls.
Given as number of true positives detected/total number of samples testing positive (percent).
PPV and NPV were calculated by using the results for healthy donors from Hong Kong [HD (HK)] and those for SARS patients (total) obtained at the same testing site in Hong Kong.
NPV, number of true negatives detected/total number of samples testing negative (percent).