The validity of a depression screening tool modified for use with Aboriginal and Torres Strait Islander people

To assess the reliability and validity of a depression screening tool--the PHQ-9Pfizer Inc. modified for use with Aboriginal and Torres Strait Islander people. We also sought to determine the prevalence of depression in a sample of Indigenous people with ischaemic heart disease (IHD).

The modified PHQ-9 was administered to a sample of Indigenous people with IHD by an Aboriginal Health Worker (AHW). Tool results were then compared with the results of a psychiatric diagnostic interview conducted by a medical practitioner. Thirty four IHD patients attending an Aboriginal Community Controlled Health Service (ACCHS) in Darwin in 2006 and 2007 participated in the study. The modified PHQ-9's sensitivity, specificity, positive and negative predictive value were calculated for major and minor depression. Chronbach's alpha of the screening test was calculated to measure internal consistency. The prevalence of depression in the study group was also determined.

The prevalence of major depression in the sample was 15.4% (95% CI 7.2%-29.7%). When assessing for major depression the modified PHQ-9 was 80% sensitive (95% CI 66.4-93.6%) and 71.4% (95% CI 56.0-86.8%) specific. A 'mini' version of the modified PHQ-9 demonstrated 100% sensitivity (95% CI 100%-100%) and 12.5% specificity (95% CI 7.0% -25.7%) Chronbach's alpha was 0.8.

The modified PHQ-9 and the mini-tool, showed promise in this setting. Further investigation with a larger number of Aboriginal and Torres Strait Islander participants is warranted.

This study has implications both for the Medicare funded Aboriginal Adult Health Checks and for program planning for Aboriginal IHD patients.