Cross classification of index test and reference standard results
| Reference standard positive | Reference standard negative | Total | |
|---|---|---|---|
| Index test positive | a (true positives) | b (false positives) | a+b (test positives) |
| Index test negative | c (false negatives) | d (true negatives) | c+d (test negatives) |
| Total | a+c (disease positives) | b+d (disease negatives) | a+b+c+d (study total) |