Page 11 - qp_17

APPENDIX 1

SENSITIVITY AND SPECIFICITY STUDY

Sensitivity is defined as the ability of a test to correctly identify the true positive (TP) rate,
whereas specificity is defined as the ability of the test to correctly identify the true negative (TN)
rate.

The positive prediction value (PPV) and negative predictive value (NPV) is defined as the
strength of a test to predict the true condition either positive or negative.

Known Condition
Positive Negative
Test Positive True Postive False Negative Positive Predictive Value
outcome Negative False Negative True Negative Negative Predictive value
Sensitivity Specificity

PROCEDURE

ANALYTE / TEST :
METHOD :
ANALYZER :

1. Prepare the statistically required sample size for this study (known positive and negative)
2. Analyze the samples.
3. Determine TP,FP,FN,TN,PPV& NPV as per table below.

Known Condition
Positive Negative
(No. of samples = ) (No. of samples = )

Positive TP = FP = PPV = [TP / (TP + FP)] x100
Test
outcome
Negative FN = TN = NPV = [TN / (FN + TN)] x100

Sensitivity Specificity
= [TP / (TP + FN)] = [TN / (FP + TN)]
x100 x100

False positive rate (%) = 1 – specificity

False negative rate 9%) = 1 - sensitivity