Table 1

2×2 table calculating the probability of illness given test result

Illness +Illness −Probability of illness given test result
Test +True positive (TP)False positive (FP)TP/(TP+FP)=PPV
Test −False negative (FN)True negative (TN)FN/(FN+TN)=1−NPV
Number with illnessNumber without illness
  • NPV, negative predictive value; PPV, positive predictive value.