Construct validity and factor structure of the Kessler-10 in South Africa

Background The Kessler Psychological Distress Scale (K-10) is a short screening tool developed to identify, with good sensitivity, non-specific psychological distress in the general population. Sensitivity and specificity of the K-10 have been examined in various clinical populations in South Africa; however, other psychometric properties, such as construct validity and factor structure, have not been evaluated. We present evidence of the prevalence and severity of psychological distress in an outpatient setting in South Africa and evaluate the internal reliability, construct validity, and factor structure of the K-10 in this population. Methods We explored prevalence estimates of psychological distress using previously established cutoffs and assessed the reliability (consistency) of the K-10 by calculating Cronbach’s alpha, item-total correlations and omega total and hierarchical coefficients. Construct validity and factor structure of the K-10 were examined through split-sample exploratory factor analysis (EFA) followed by confirmatory factor analysis (CFA), comparing several theoretical models and the EFA. Results Overall, there was low prevalence of psychological distress in our sample of 2591 adults, the majority of whom were between the ages of 18–44 (77.7%). The K-10 showed good construct validity and reliability, with a Cronbach’s alpha of 0.84 and omega total of 0.88. EFA yielded a four-factor solution with likely measurement artifacts. CFA showed that the four-factor model from EFA displayed the best comparative fit indices, but was likely overfitted. The unidimensional model with correlated errors was deemed the best fitting model based on fit indices, prior theory, and previous studies. Conclusion The K-10 displays adequate psychometric properties, good internal reliability, and good fit with a unidimensional-factor structure with correlated errors. Further work is required to determine appropriate cutoff values in different populations and clinical subgroups within South Africa to aid in determining the K-10’s clinical utility

Measuring psychological distress using the K10 in Kenya

Background: The Kessler psychological distress scale (K10) is a brief screening tool that assesses psychological distress in both clinical and epidemiological settings. Despite wide applicability of the K10 globally, there are no data on psychometric properties of the K10 in Kenya. This study investigated the reliability, factor structure, and construct validity of the K10 as a measure of psychological distress among adults in Kenya. Methods: A total of 2556 adults attending 11 outpatient clinics in the western and coastal regions of Kenya without a history or clinical diagnosis of psychotic disorders were included. Data were collected on demographic characteristics of the participants and the K10. Internal consistency was evaluated using Cronbach’s alpha. Construct validity and factor structures of the K10 were evaluated using both exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) approaches. Results: The mean K10 score was 3.4 and Cronbach’s alpha was 0.85, indicating good internal consistency (reliability). EFA resulted in a two-factor solution that accounted for 67.6% of variance. CFA results indicated that a unidimensional model with correlated errors best fit the data. Limitations: The K10 was only administered to a control group of our study population, which had low levels of psychological distress. Conclusion: The K10 has good construct validity and reliability for use as a broad measure of psychological distress in Kenyan adults and may be useful in general medical setting to assess anxiety and depressive disorders

Cross-country variations in the reporting of psychotic symptoms among sub-Saharan African adults: A psychometric evaluation of the Psychosis Screening Questionnaire

Background: Self-reporting of psychotic symptoms varies significantly between cultures and ethnic groups. Yet, limited validated screening instruments are available to capture such differences in the African continent. Methodology: Among 9,059 individuals participating as controls in a multi-country case-control study of the genetic causes of psychosis, we evaluated the psychometric properties of the Psychosis Screening Questionnaire (PSQ). We applied multi-group confirmatory factor analysis and item response theory to assess item parameters. Results: The overall positive endorsement of at least one item assessing psychotic symptoms on the PSQ was 9.7%, with variability among countries (Uganda 13.7%, South Africa 11%, Kenya 10.2%, and Ethiopia 2.8%). A unidimensional model demonstrated good fit for the PSQ (root mean square error of approximation = 0.009; comparative fit index = 0.997; and Tucker-Lewis Index = 0.995). Hypomania had the weakest association with single latent factor (standardized factor loading 0.62). Sequential multi-group confirmatory factor analysis demonstrated that PSQ items were measured in equivalent ways across the four countries. PSQ items gave more information at higher levels of psychosis, with hypomania giving the least discriminating information. Limitations: Participants were recruited from general medical facilities, so findings may not be generalizable to the general population. Conclusion: The PSQ demonstrated a unidimensional factor structure in these samples. Items were measured equivalently across all study settings, suggesting that differences in prevalence of psychotic symptoms between countries were less likely to represent measurement artifact. The PSQ is more reliable in screening for psychosis in individuals with higher degrees of psychotic experiences-hypomania excluded-and might decrease the false-positive rate from mild nonspecific psychotic experiences

Increasing diversity in genomics requires investment in equitable partnerships and capacity building

Calls for diversity in genomics have motivated new global research collaborations across institutions with highly imbalanced resources. We describe practical lessons we have learned so far from designing multidisciplinary international research and capacity-building programs that prioritize equity in two intertwined programs — the NeuroGAP-Psychosis research study and GINGER training program — spanning institutions in Ethiopia, Kenya, South Africa, Uganda and the United States

Low-coverage sequencing cost-effectively detects known and novel variation in underrepresented populations

Background: Genetic studies of biomedical phenotypes in underrepresented populations identify disproportionate numbers of novel associations. However, current genomics infrastructure--including most genotyping arrays and sequenced reference panels--best serves populations of European descent. A critical step for facilitating genetic studies in underrepresented populations is to ensure that genetic technologies accurately capture variation in all populations. Here, we quantify the accuracy of low-coverage sequencing in diverse African populations. Results: We sequenced the whole genomes of 91 individuals to high-coverage (\u3e20X) from the Neuropsychiatric Genetics of African Population-Psychosis (NeuroGAP-Psychosis) study, in which participants were recruited from Ethiopia, Kenya, South Africa, and Uganda. We empirically tested two data generation strategies, GWAS arrays versus low-coverage sequencing, by calculating the concordance of imputed variants from these technologies with those from deep whole genome sequencing data. We show that low-coverage sequencing at a depth of ≥4X captures variants of all frequencies more accurately than all commonly used GWAS arrays investigated and at a comparable cost. Lower depths of sequencing (0.5-1X) performed comparable to commonly used low-density GWAS arrays. Low-coverage sequencing is also sensitive to novel variation, with 4X sequencing detecting 45% of singletons and 95% of common variants identified in high-coverage African whole genomes. Conclusion: These results indicate that low-coverage sequencing approaches surmount the problems induced by the ascertainment of common genotyping arrays, including those that capture variation most common in Europeans and Africans. Low-coverage sequencing effectively identifies novel variation (particularly in underrepresented populations), and presents opportunities to enhance variant discovery at a similar cost to traditional approaches

Factor structure and item response of psychosis symptoms among Kenyan adults

Background: The aim of this study was to evaluate the construct validity of the psychosis module of the Mini International Neuropsychiatric Interview version 7.0.2 (MINI-7). Method: We utilized data collected from 2738 participants with a primary psychotic or bipolar disorder. Par- ticipants were drawn from two Kenyan sites of a large multi-center neuropsychiatric genetic study. The factor structure of the MINI-7 psychosis items were explored using confirmatory factor analyses (CFA) and Item Response Theory approach, for the full sample and by gender. Results: The CFA revealed that a 1-factor model provided adequate fit for the MINI-7 psychosis items for the full sample (x2 = 397.92, df = 35, p \u3c .0001; RMSEA = 0.06; CFI = 0.92; TLI = 0.90) as well as for the female (x2 = 185.16.92, df = 35, p \u3c .0001; RMSEA = 0.06; CFI = 0.93; TLI = 0.91) and male groups (x2 = 242.09, df = 35, p \u3c .0001; RMSEA = 0.06; CFI = 0.92; TLI = 0.89). Item thresholds for the full sample, and female and male groups were highest for ‘odd beliefs’ ( 1.42, 1.33, and 1.51 respectively) and lowest for ‘visual hallucina- tions’ ( 0.03, 0.04, and 0.01 respectively). Limitations: Our study used a hospital-based population, which may have excluded patients with milder psychotic symptoms. Findings may therefore not be generalizable to the community setting. Conclusions: Our findings indicate good construct validity of the MINI-7 psychosis module, and provides support for use of the tool in diagnosing psychotic disorders in clinical settings in Keny

Traumatic experiences assessed with the life events checklist for Kenyan adults

Background: Life Events Checklist (LEC-5) has been widely used to assess for exposure to potentially traumatic life events (PTEs), but its psychometric properties have not been evaluated in Kenya. The objectives of this study were to determine the frequency and types of PTEs within this setting and to examine the construct validity of LEC-5 in Kenya. Methods: The LEC-5 was administered to 5316 participants in the ongoing multisite case–control study of Neuropsychiatric Genetics of African Populations-Psychosis. We used exploratory factor analysis to assess LEC-5 structure, and conducted confirmatory factor analyses to compare these results with two other models: a six- factor model based on the only prior EFA of the LEC and a theoretical seven-factor model. Results: The majority (63.4% overall and 64.4% of cases and 62.4% of controls) of participants had experienced at least one PTE in their lifetime. Results of the exploratory factor analyses for LEC-5 yielded a seven-factor solution with eigenvalues greater than one, accounting for 55.3% of the common variance. Based on confir- matory factor analyses, all three models had good fit for our sample, but the theoretical seven-factor model had the best fit. Limitations: The study did not assess if the participants perceived experiences as traumatic, we did not carry out test retest reliability or and we did not consider cultural variations in perception of trauma. Conclusion: This study provides evidence of a high prevalence of traumatic life events and for the construct validity of LEC-5 in assessing PTE exposures in a Kenyan setting

Cross-cultural equivalence of the Kessler Psychological Distress Scale (K10) across four African countries in a multi-national study of adults

The Kessler Psychological Distress Scale (K10) has been widely used to screen psychological distress across many countries. However, its performance has not been extensively studied in Africa. The present study sought to evaluate and compare measurement properties of the K10 across four African countries: Ethiopia, Kenya, Uganda, and South Africa. Our hypothesis is that the measure will show equivalence across all.Data are drawn from a neuropsychiatric genetic study among adult participants (N = 9179) from general medical settings in Ethiopia (n = 1928), Kenya (n = 2556), Uganda (n = 2104), and South Africa (n = 2591). A unidimensional model with correlated errors was tested for equivalence across study countries using confirmatory factor analyses and the alignment optimization method. Results displayed 30 % noninvariance (i.e., variation) for both intercepts and factor loadings across all countries. Monte Carlo simulations showed a correlation of 0.998, a good replication of population values, indicating minimal noninvariance, or variation. Items “so nervous,” “lack of energy/effortful tasks,” and “tired” were consistently equivalent for intercepts and factor loadings, respectively. However, items “depressed” and “so depressed” consistently differed across study countries (R2 = 0) for intercepts and factor loadings for both items.The K10 scale likely functions equivalently across the four countries for most items, except “depressed” and “so depressed.” Differences in K10 items were more common in Kenya and Ethiopia, suggesting cultural context may influence the interpretation of some items and the potential need for cultural adaptations in these countries