In evaluating HbA1c threshold performance for retinopathy, what does a reported 88% specificity indicate?

In evaluating HbA1c threshold performance for retinopathy, what does a reported 88% specificity indicate?

• A. The threshold has 88% specificity
• B. The threshold has 88% sensitivity
• C. The threshold has 88% positive predictive value
• D. The threshold has 88% negative predictive value

Answer: (A)

Specificity tells you how good the threshold is at ruling out disease in people who do not have it. An 88% specificity means that among those without retinopathy, 88% will have a negative HbA1c result at that threshold and be correctly identified as not having retinopathy. The remaining 12% would be false positives at this threshold—they would be flagged as at risk even though they don’t have retinopathy. This differs from sensitivity (how well the threshold detects those with the disease) and from predictive values, which depend on how common retinopathy is in the tested group.

Specificity tells you how good the threshold is at ruling out disease in people who do not have it. An 88% specificity means that among those without retinopathy, 88% will have a negative HbA1c result at that threshold and be correctly identified as not having retinopathy. The remaining 12% would be false positives at this threshold—they would be flagged as at risk even though they don’t have retinopathy. This differs from sensitivity (how well the threshold detects those with the disease) and from predictive values, which depend on how common retinopathy is in the tested group.