Notes on verification

Confirmed by ISS Epicentro/Passi documentation citing Kroenke et al. 2003, the original PHQ-2 validation study. Minor discrepancy (90% vs 92%) exists across secondary sources reporting the same original study, but the 90% figure used by the Italian surveillance system is well corroborated. [tier=gold indep_score=1.0 clusters=3 claim_tier=notable | framework convergence=single on Kroenke et al. 2003 PHQ-2 validation study (upstreams: Kroenke K, Spitzer RL, Williams JBW (2003) Med Care 41:1284-1292) — publishers independent, evidence may not be | kind=empirical eligibility=high (extractor: empirical/medium)]