Application of the age of onset of problem drinking based on a single item from the CDP classified 47 patients as EOAs and 87 patients as LOAs. Cross-tabulation of the SCID-derived age of onset and the CDP-derived age of onset resulted in 95% agreement (κ = 0.89) in the classification of EOAs and LOAs. Of the 7 patients (5%) classified differently by the two methods, 3 were classified as EOAs with the SCID and as LOAs with the CDP and 4 patients were classified as LOAs with the SCID and as EOAs with the CDP. Subtypes derived from the single-item age of onset and those obtained using the k-means clustering method showed modest concordance (κ = 0.27), similar to that seen between the SCID age of onset and the k-means cluster subtypes.
