Research report
The comparative validity of screening scales for postnatal common mental disorder in Kintampo, Ghana

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Abstract

Background

There have been few attempts formally to validate screening measures for postnatal common mental disorder in low income country settings. We have investigated the comparative validity of three different screening approaches in a community-based study in Kintampo, Ghana.

Method

160 women aged 15–45 years, and 5–11 weeks postpartum were first screened using the Self-Report Questionnaire (SRQ-20), with oversampling of higher scorers. The other test assessments were the Edinburgh Postnatal Depression Scale (EPDS) and the Patient Health Questionnaire (PHQ-9). Criterion validity was measured against the Comprehensive Psychopathological Rating Scale (CPRS), and concurrent validity against the WHO Disability Assessment Schedule. A sub-sample (n = 40) was re-interviewed 2 weeks later for test–retest reliability.

Results

Internal consistency (Cronbach's Alpha) was equivalent across all three test scales; EPDS (0.79), SRQ-20 (0.78) and PHQ-9 (0.79). Test–retest reliability was better for PHQ-9 (ICC 0.75) than for the EPDS (0.51). For criterion validity the PHQ-9 (AUROC 0.90 (0.81–0.98)), was superior to the SRQ-20 (0.74 (0.62–0.86)) and the EPDS ((0.84 (0.76–0.92). Youden's Index was also superior for PHQ-9. Item analysis revealed that a mixture of somatic and cognitive symptoms best discriminated between cases and non-cases for all three scales.

Limitations

Inability to ascertain inter-rater reliability, order effects and possible loss of technical equivalence due to item modifications.

Conclusions

The evidence for the validity, reliability, and superiority of the PHQ-9 over other screening assessments has been extended. The PHQ-9 is short, easy to administer and acceptable to a largely illiterate population of Ghanaian women, 5 to 11 weeks post partum.

Section snippets

Background

Postnatal common mental disorder (CMD) comprises a group of conditions including depression, anxiety and somatisation disorders. Postnatal depression has been most extensively studied; the average prevalence from studies carried out in economically developed countries was 13% (95% CI 12.3 to 13.4) (O'Hara and Swain, 1996). Its public health significance is clearly established, with serious long-term consequences for maternal mental health(Kumar and Robson, 1984) and the cognitive and social

Setting and participants

The ObaapaVitA study is a cluster-randomised, double-blind, placebo-controlled trial investigating the impact of weekly vitamin A supplements on maternal mortality in rural Ghana. ObaapaVitA has established 4-weekly visits by field workers to all women aged 15 to 45 years living in six districts in the Brong Ahafo region of Ghana, with data collected on all pregnancies, births, deaths and migrations. Over 100,000 women are currently participating in the trial and around 14,000 births occur each

Results

One hundred and sixty women were recruited for the validation study. Mean age was 27.1 years (range 16–45, SD 6.5). They were all between 5 and 11 weeks postpartum (mean 8.3 weeks, SD 1.3). According to the CPRS global severity rating, 117 (73.1%) had no signs of illness (CPRS rating = 0), 25 (15.6%) had minimal or doubtful illness (rating = 1), 18 (11.3%) moderate and definite illness (rating = 2), and none had severe or incapacitating illness (rating = 3). Therefore 18 women (11.3%) met the gold

Discussion

We set out to compare the reliability and validity of two measures designed to screen for depression (PHQ-9 and EPDS) and one designed to screen for psychological morbidity (SRQ-20) for the detection of common mental disorders in the postpartum period, in a Ghanaian rural setting. While all three scales were adequately internally consistent, the PHQ-9 showed better test–retest reliability than the EPDS and better criterion validity than either the EPDS or the SRQ-20. All three scales needed to

Role of funding source

Funding for this study was provided by the Wellcome Trust, as a Master's Level Fellowship for Benedict Weobong. The Wellcome Trust had no further role in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication.

Conflict of interest

All authors declare that they have no conflict of interest.

Acknowledgments

We thank all the women who participated in this validation study for their time and high sense of dedication they displayed. We also are very grateful to the director and staff of the District Health Management Teams of Wenchi and Kintampo for their support during the pilot phase of this study. We would like to especially recognize the immense contribution of Awudu Issaka who was part of the data collection team.

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