This validation study investigated the internal consistency, concurrent, construct and criterion validity of the CES-D-10 among Zulu, Xhosa and Afrikaans-speaking populations. These languages are the most commonly spoken in South Africa, according to the 2011 census : 22.7% of the South African population speaks Zulu, 16.0% speaks Xhosa and 13.5% speaks Afrikaans. The study consisted of face-to-face interviews which included (1) basic demographic and economic questions; (2) depression and functioning screening instruments; and (3) the Mini International Neuropsychiatric Interview (MINI) 6.0 (Major Depressive Episode) .
Demographic and socio-economic information
Basic demographic and socio-economic information covered age, gender, population group, marital status, education, employment status, personal income and assets owned. Household economic measures included type of dwelling, number of household members, as well as access to electricity, water and sanitation.
Centre for Epidemiological Studies Depression Scale (CES-D-10)
The CES-D-10 is a 10-item Likert scale questionnaire assessing depressive symptoms in the past week . It includes three items on depressed affect, five items on somatic symptoms, and two on positive affect. Options for each item range from “rarely or none of the time” (score of 0) to “all of the time” (score of 3). Scoring is reversed for items 5 and 8, which are positive affect statements. Total scores can range from 0 to 30. Higher scores suggest greater severity of symptoms.
Patient Health Questionnaire – 9 item (PHQ-9)
The PHQ-9 is a 9-item screening measure for depression, where participants are asked to rate how often they were bothered by specific symptoms over the last two weeks . Each item is scored from 0 (“Not at all”) to 3 (“Nearly every day”). Higher scores indicate greater symptoms of depression. The PHQ-9 has been validated in a range of settings and populations in low and middle-income countries , including South Africa .
Mini International Neuropsychiatric Interview (MINI) 6.0, Major Depressive Episode module
The presence of major depression was determined using the MINI 6.0 , which uses the DSM-IV criteria for major depressive episodes. It has been used as a gold standard in many cross-cultural studies, including in HIV-positive patients in South Africa [31, 32].
WHO Disability Assessment Schedule (WHODAS 2.0) (12-item)
Functional impairment was assessed using the WHODAS 2.0 . It comprises 12 items with response options ranging from ‘No difficulty’ to ‘Extreme difficulty or unable to do’. The item-response-theory (IRT) based scoring was used, as set out in the WHODAS 2.0 Manual : scores are percentages, with higher percentages suggesting greater impairment. The WHODAS 2.0 has undergone extensive validation, and has good reliability and validity across cultures and population groups .
All sections of the questionnaire, including the MINI assessment, were translated into Xhosa, Afrikaans and Zulu, and back translated to English, by six independent translators. The research team worked with the translators to assess the accuracy of each item, and to resolve discrepancies where these arose.
Three samples were recruited, one for each language. Given that the prevalence of individuals screening ≥10 or ≥15 on the CES-D-10 in the first wave of NIDS was 28 and 8% respectively in the Western Cape, and 32 and 5% in KwaZulu Natal,Footnote 1 it was determined that a total of 300 participants per sample would be sufficient to analyse higher CES-D-10 scores, and have enough power to assess criterion validity. The sample size of validation studies included in a recent meta-analysis of the PHQ-9  usually ranged from 150 to 600. The proposed sample therefore falls within the range of validation studies considered methodologically strong.
Participants were recruited from two districts in South Africa: the City of Cape Town metro district and Ethekwini district in KwaZulu Natal, which encompasses both rural and urban areas. The ‘small area level’ (SAL) was used as the primary sampling unit from which to select households in the two districts. The SAL is the lowest level of geographic unit for which Census data is publically available, and is a manageable size in terms of population and land area. Population sizes vary across SALs, but usually range between 400 and 1000 individuals.
Only SALs classified as residential were included in the sampling base. SALs were selected for inclusion using systematic sampling, based on data from StatsSA. SALs were stratified by the most common home language, main population group (White, Black, Coloured, Indian), type of area (rural/urban) and most common income bracket. In South Africa, the term ‘coloured’ is not considered critical, and is used to describe an ethnic group composed primarily of persons of mixed race.
A total of six participants were recruited per SAL, with a maximum of two participants per household. The first household in each SAL was selected using a random starting point (created using a sampling algorithm on the Geographic Information System). Every third household was then selected from this starting point. Non-dwelling structures, such as shops, churches and museums, were skipped. Households were still included in the three count method when members were not at home or refused to participate.
This process was repeated until six participants per SAL were reached. If this could not be reached in a particular SAL, then the nearest predetermined oversampled SAL with the same settlement pattern was attempted, in order to reach the full complement of six participants. A total of 75 SALs were selected per sample, including an additional 50% of oversampled SALs.
To be eligible, participants had to be aged 15 years or more, and be able to provide consent. Their home language had to be Xhosa, Afrikaans or Zulu, depending on the district, and be considered household members. This was defined as relatives or non-relatives who lived under the same roof or within the same compound, shared resources, and slept in the house for at least four nights a week. Live-in domestic workers and lodgers were regarded as separate households.
All fieldworkers conducting the interviews received one week of training by a registered counsellor (TD), on mental illness, administration of the tools, and methodological procedures. The first part of the training consisted of general psychoeducation on symptoms of depression and available treatments, and open discussions on the fieldworkers’ knowledge or experience of depression. The second part of the training included a back-translation of the translated MINI, as a cognitive testing exercise, to ensure the fieldworkers had a full understanding of the concepts of symptoms assessed in the MINI, and to ensure these corroborated with the translators’ translation. Fieldworkers were then trained to administer the MINI and the other screening tools, facilitated by role plays during which inter-rater reliability was also informally assessed. The depth of training on depression, in addition to the tool itself, was essential to ensure the accuracy of the fieldworkers’ diagnostic assessments, and ensure that the data collected were robust and the interpretation of results reliable. Finally, TD spent three days with each fieldwork team at the start of data collection, shadowing all interviews conducted to monitor the quality of the MINI assessment and of the accuracy of diagnoses made.
Xhosa and Afrikaans speaking participants were recruited from the City of Cape Town metro district and Zulu speaking participants from the Ethekwini district. Each sample of 300 participants was recruited by one team, comprising of two experienced, trained fieldworkers. Aerial maps of the SALs were printed and provided to the fieldworkers to navigate the SALs. The starting point for the SAL and non-dwelling structures were indicated on the maps. Fieldworkers first approached the households to determine that the language criterion was met. If a household member was present, eligible and agreed, he or she was asked to provide a list of all eligible members in the household, even if they were not present at the time of the visit. Two participants were then randomly selected, using the Dice method: a number was assigned to each eligible household member and an 18-faced dice was thrown to select the assigned number for individuals to be recruited. Appointments were made if selected individuals in the household were not present. A missed appointment was considered as a refusal.
Data were collected electronically, with the use of mobile devices. The interview was administered by the same fieldworkers involved in the recruitment process. The CES-D-10, PHQ9 and WHODAS 2.0 were administered separately from the socio-economic section and MINI 6.0 depression module, and by a different fieldworker, to avoid response bias. Each section of the interview was conducted in a private area of the participant’s home, away from other household members and the second fieldworker. Minors completed the interview in the presence of the consenting caregiver. The full interview lasted approximately 45 min.
The data collected were transferred to Stata version 13, where analyses were conducted separately for each sample. Descriptive statistics were used to describe the socio-demographic characteristics of the participants, their screening scores and depression diagnosis. A review of kurtosis and skewness suggested that none of the scores on the CES-D-10, PHQ-9 or WHODAS 2.0 were normally distributed, so non-parametric tests and medians (interquartile range; IQR) were reported throughout the analysis. Probability weights were calculated to estimate the population-level prevalence of depression, taking into account the selection of eligible SALs among the districts, and the probability of a household being selected within an SAL and of an individual being selected within a household. Non-parametric independent tests were used to compare CES-D-10 scores between depressed and non-depressed participants. The internal reliability of the CES-D-10 and PHQ-9 were assessed using Cronbach’s Alpha. The CES-D-10’s convergent validity was determined by assessing its correlation with the WHODAS 2.0 and the PHQ-9. An exploratory factor analysis with varimax rotation was applied to investigate the construct validity of the CES-D-10, using the Kaiser Test and scree plot to identify latent dimensions of the scale. Finally, Receiver Operating Characteristics (ROC) curves were used to examine the CES-D-10 and PHQ-9’s criterion validity against the MINI 6.0. Optimal cut-off scores were identified as the best balance between sensitivity and specificity values, giving equal weight to both measures. The area under the ROC curve for the CES-D-10 was compared to that of the PHQ-9 using the DeLong method .
This study was approved by the University of Cape Town’s Health Sciences Faculty Human Research Ethics committee (REF: 209/2016). Consent and assent forms were translated in all three languages and completed by all participants who agreed to participate. A R20 supermarket voucher was given to each participant, at the end of the interview. Participants who were diagnosed with depression were given a brochure on depression, and a list of local non-governmental organisations and toll-free numbers they could contact for counselling. Participants who reported suicidal behaviour were referred to the mental health nurse at a primary health care clinic of their choice. Suicide behaviours were considered present if participants answered ‘yes’ to the MINI 6.0 item (“Did you repeatedly consider hurting yourself, feel suicidal or wish that you were dead? Did you attempt suicide or plan a suicide?”), or answered ‘several days’ or more to PHQ9 item (“Thoughts that that you would be better off dead or of hurting yourself in some way”).