Labs and Diagnostics

Nurse practitioners must independently select, order, and interpret diagnostic studies using evidence-based reasoning. Diagnostic accuracy depends on understanding pretest probability, which is the likelihood of disease before testing, combined with test characteristics including sensitivity, specificity, and predictive values. Sensitivity measures a test's ability to correctly identify those with the disease (true positive rate), while specificity measures its ability to correctly identify those without the disease (true negative rate). Advanced lab panels including thyroid function, iron studies, lipid profiles, and tumor markers require interpretation within clinical context, as isolated abnormal values frequently occur in the absence of disease.