CDC Kerala 11: Diagnosis of autism among children between 2 and 6 y--comparison of CARS against DSM-IV-TR.

Objectives: To compare diagnosis of childhood autism using CARS cut off scores of ≥30 and the new Indian cut off scores of ≥33 against the gold standard DSM-IV-TR criteria available during the study period 2009-10.

Methods: The study was conducted at the autism clinic of Child Development centre (CDC), Kerala. Two hundred consecutive children between 2 and 6 y with symptoms suggestive of autism were administered both CARS by a trained developmental therapist and DSM-IV-TR by a developmental pediatrician on the same day, both blind to the test results of each other. Diagnosis of autism using CARS cut off scores 30 and above, as suggested in original tool administration manual and 33 and above, as suggested for diagnostic use in Indian population was compared with DSM-IV-TR diagnosis. Data was analyzed using SPSS (version 19.0) software.

Results: Against DSM-IV-TR diagnosis as gold standard, the new CARS cut off scores ≥33 had a higher Specificity (74.3%), Positive predictive value (PPV) (81.9%), Positive likelihood ratio (LR) (2.66) and Negative LR (0.43), but had a lower Sensitivity (68.3%), Negative predictive value (NPV) (57.9%) and accuracy (70.5%), as compared to the cut off scores of ≥30.

Conclusions: The CARS prevalence of autism for cut off points ≥30 and ≥33 was 71.5 and 52.5% respectively against 63% prevalence by DSM-IV-TR.