PRAME immunohistochemistry for melanoma diagnosis: A STARD‐compliant diagnostic accuracy study

Preferentially expressed antigen in melanoma (PRAME) is a tumor-associated antigen that is frequently expressed in cutaneous melanoma and can be evaluated by immunohistochemistry. Earlier studies on PRAME utilized case-control study designs that may misestimate diagnostic accuracy and lack generalizability.Using retrospective cohort selection, a cross-sectional study of diagnostic accuracy of PRAME was conducted according to standards for reporting diagnostic accuracy studies requirements.Mean PRAME positive fraction was higher in 42 malignant melanocytic lesions than 101 benign melanocytic lesions (0.71 ± 0.30 vs. 0.13 ± 0.20, p < 0.01). Receiver operating characteristic curve showed the test was effective (area under the curve = 0.90). Global PRAME 4+ scores (>75%) were associated with sensitivity of 0.63, specificity of 0.97, accuracy of 0.87, and excellent interrater concordance (Kappa = 0.83). Lower cutoffs for PRAME of 2+ (>25%) and 3+ (>50%) produced higher joint sensitivity/specificity (Youden index) than PRAME 4+, but lower accuracy.PRAME as it is used in clinical practice is an effective test for melanoma. PRAME is best used as an ordinal variable to calculate the posttest probability of melanoma. PRAME ≤25% (0/1+) favors nevus, PRAME 26%-75% (2/3+) is noncontributory, and PRAME >75% (4+) favors melanoma.