The validation study and application of stratum-specific likelihood ratios in the Chinese version of SPAN

The Davidson Trauma Scale (DTS) is a validated self-rating scale used in the diagnosis of post-traumatic stress disorder (PTSD). A shorter version of the DTS was developed to serve as a diagnostic screening tool. A four-item scale, the SPAN (named for its principal four items: Startle, Physiological arousal, Anger, and Numbness), was then developed. This report investigates the psychometric validation of the Chinese version of the SPAN (SPAN-C). Subjects were drawn from a sample of 210 survivors of the September 21, 1999 Chi-Chi Earthquake. The scale showed good internal consistency (Cronbach's alpha= 0.77) and test-retest reliability (r = 0.90). Concurrent validity was obtained against the clinical diagnostic interview, with a diagnostic accuracy of 0.8 at a SPAN-C score of 5. The recommended stratum-specific likelihood ratios were 0.04 (95% confidence interval [CI], 0.02 to 0.07) for the score range of 0 to 2, 0.93 (95% CI, 0.51 to 1.71) for the score range of 3 to 4, 2.31 (95% CI, 1.17 to 4.57) for the score range of 5 to 6, and 5.23 (95% CI, 3.12 to 8.78) for scores above 7. The psychometric strength of the SPAN-C indicates its reliability for future use, particularly for screening for subjects with a possible diagnosis of PTSD.