Clinical meaning
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.
Diagnosis & workup
Diagnostics & workup: - Thyroid panel: TSH 0.4-4.0 mIU/L, Free T4 0.8-1.8 ng/dL, Free T3 2.3-4.2 pg/mL; elevated TSH with low free T4 indicates primary hypothyroidism - Iron studies: Serum iron 60-170 mcg/dL, TIBC 250-370 mcg/dL, Ferritin 12-150 ng/mL (female) 12-300 ng/mL (male), Transferrin saturation 20-50% - Lipid panel: Total cholesterol less than 200 mg/dL, LDL less than 100 mg/dL (less than 70 for high-risk), HDL greater than 40 mg/dL (male) greater than 50 mg/dL (female), Triglycerides less than 150 mg/dL - HbA1c: less than 5.7% normal, 5.7-6.4% prediabetes, 6.5% or greater diabetes; each 1% change represents approximately 28-30 mg/dL change in average glucose - Imaging selection: X-ray for initial bone and chest evaluation, CT for acute trauma and pulmonary embolism, MRI for soft tissue and neurological assessment, Ultrasound for pregnancy, gallbladder, and vascular studies