Researchers are evaluating the performance measures of a novel newborn screening test for an autosomal recessive condition that may be performed 24 to 72 hours after birth. An excerpt of the results is presented below: Which of the following is the most accurate statement regarding these data?
A)The specificity of the test is greater at 24 hours after birth than at 72 hours after birth
B)The test is an excellent screening test for the detection of the autosomal recessive condition
C)The test is less sensitive at 24 hours after birth than at 72 hours after birth
D)The test performs best when screening newborns without the autosomal recessive condition
E)The test performs worse at 24 hours after birth than at 72 hours after birth

Question

Researchers are evaluating the performance measures of a novel newborn screening test for an autosomal recessive condition that may be performed 24 to 72 hours after birth.  An excerpt of the results is presented below: Which of the following is the most accurate statement regarding these data?
A)The specificity of the test is greater at 24 hours after birth than at 72 hours after birth
B)The test is an excellent screening test for the detection of the autosomal recessive condition
C)The test is less sensitive at 24 hours after birth than at 72 hours after birth
D)The test performs best when screening newborns without the autosomal recessive condition
E)The test performs worse at 24 hours after birth than at 72 hours after birth

Quizplus · Accepted Answer

Explanation: 11ec2b69_c105_8e9e_8f63_279a72a7f23d_MD0005_00 Performance estimations and related 95% confidence intervals (CIs) of the new screening test were as follows: Sensitivity was 0.58 (95% CI: 0.07-0.65) and 0.61 (95% CI: 0.30-0.92) at 24 and 72 hours after birth, respectively. Because the CIs overlap, there is no statistically significant difference in sensitivity at 24 and 72 hours after birth (Choice C). Specificity was 0.87 (95% CI: 0.82-0.92) and 0.85 (95% CI: 0.79-0.91) at 24 and 72 hours after birth, respectively. Because the CIs overlap, there is no statistically significant difference in specificity at 24 and 72 hours after birth (Choice A). Similarly, positive predictive value (PPV) was 0.16 (95% CI: 0.09-0.23) and 0.18 (95% CI: 0.05-0.31) at 24 and 72 hours after birth, respectively, and negative predictive value (NPV) was 0.94 (95% CI: 0.89-0.96) and 0.96 (95% CI: 0.92-1.00) at 24 and 72 hours after birth, respectively. Because the CIs overlap, there is no statistically significant difference in these measures at 24 and 72 hours after birth. Given the lack of statistically significant differences, the overall performance of the test appears similar at 24 and 72 hours after birth, with no evidence that the test performs worse at 24 hours than at 72 hours (Choice E). The specific values of the measures help clarify test performance. This test has low PPV (probability of disease in those who test positive) of 0.16 and 0.18 and low sensitivity (probability of positive test result in those with disease) of 0.58 and 0.61. Conversely, it has high NPV (probability of no disease in those who test negative) of 0.94 and 0.96 and high specificity (probability of negative test result in those without disease) of 0.85 and 0.87. The high specificity and NPV suggest that the test performs best when screening newborns who do not have the condition because high specificity means that newborns without the condition have a high probability of a negative test result and high NPV means that newborns with a negative test result have a high probability of not having the condition. (Choice B) Screening tests ideally have a high sensitivity to minimize failure to identify affected newborns (ie, minimize false negatives), typically at the cost of reporting more false positives. The given sensitivity values (ie, 0.58, 0.61) are too low to be considered adequate for a screening test. Educational objective: A screening test with high specificity and negative predictive value will be highly accurate in identifying individuals with no disease.

Researchers Are Evaluating the Performance Measures of a Novel Newborn