A family physician is evaluating the utility of a rapid antigen detection test for streptococcal pharyngitis in a community clinic. Over the past year, the physician notices that during the summer months, when streptococcal pharyngitis is rare in the community, a positive rapid test frequently turns out to be a false positive upon throat culture confirmation. However, during the winter school months, when the infection is highly prevalent, a positive rapid test is almost always confirmed as a true positive by culture. Assuming the intrinsic diagnostic properties of the rapid test remain constant, which of the following statistical parameters of the test is highest during the winter months compared to the summer months?
- Positive predictive valueCevap
- BNegative predictive value
- CSensitivity
- DSpecificity
- ELikelihood ratio of a positive test
Cevap
Positive predictive value
Positive predictive value (PPV) is defined as the probability that a patient with a positive test result truly has the disease. Mathematically, it is expressed as . Unlike sensitivity and specificity, PPV is directly dependent on the prevalence of the disease in the population being tested. When the disease prevalence increases (e.g., during the winter outbreak), the absolute number of true positives in the population increases relative to the number of false positives. As a result, a positive test result is much more likely to represent true disease, leading to a higher PPV.
Adım Adım Çözüm
Anahtar Kavram
The relationship between disease prevalence and positive predictive value.
Tahmini Süre:45s