[Cognitive screening test: short and long version].
Three versions of the Cognitive Screening Test (CST), varying in length from seven to 20 items, are compared using the original data. The shortest version, the CST-7, is not inferior to the longer CST-14 and CST-20. Various psychometric properties are compared. According to the Mokken nonparametric IRT scaling technique, all three CST versions can be considered unidimensional. The Mokken scaling indices H and rho hardly differ in the three versions of the CST. The alpha indices from Classical Test Theory are also very comparable, as is the very good sensitivity and specificity (around 95%). Age and gender have no significant effect on the classification success of the CST-7. Cross-validation of the promising properties of this very short screening instrument is recommended.