This can be calculated from the given study design - it is the proportion of true positives (those correctly diagnosed with the disease) out of all actual cases of disease. The study provides data on both true positives (those with GAS on culture) and false negatives (those symptomatic but culture negative). Therefore, sensitivity can be determined.

The study design does not provide enough information to calculate specificity. However, it is not the correct answer because both specificity and PPV cannot be calculated, and of the two, the question asks for the test that cannot be 'evaluated'. In statistical terms, 'evaluation' commonly refers to estimating predictive values (PPV and NPV) more than simply calculating sensitivity or specificity.

Positive Predictive Value (PPV) depends on the prevalence of the disease and has to be calculated from diagnostic testing among a group of people with the disease. In the study, the physician has only sampled a group of individuals who have been diagnosed with the disease (true positives) and a group of individuals who were symptomatic but all were negative for the disease (false negatives), hence, since false positives are unknown, PPV cannot be determined.

This can be calculated from the given study design - it is the proportion of true negatives (those correctly diagnosed as not having the disease) out of all those who do not have the disease. The study provides data on true negatives (those symptomatic but culture negative) and true positives (those with GAS on culture). Therefore, NPV can be determined.