Epidemiological data on systemic lupus erythematosus in Native sub-Saharan Africans

Value of the data

• This article provides an in-depth analysis of the data on systemic lupus erythematosus in Native sub-Saharan Africans.
• These data are beneficial for health professionals and researchers involved in systemic lupus erythematosus management and research, as well as local health authorities.
• As these data inform on the burden and management of systemic lupus erythematosus in Native sub-Saharan Africans, they may be used to increase awareness for systemic lupus erythematosus in sub-Saharan Africa and serve as accurate basis for building capacity for research and management of systemic lupus erythematosus in Native sub-Saharan Africans.

1. Data

In the recently published study, there are a number of tables that illustrate the data collected during the analysis. Table 1 reports the summary statistics from the meta-analysis of the hospital prevalence of systemic lupus erythematosus among Native sub-Saharan Africans, whereas Table 2 summarizes the studies reporting on the mortality rate in Native sub-Saharan Africans with systemic lupus erythematosus.  Table 3 reports the prevalence of comorbidities and complications in Native sub-Saharan Africans with systemic lupus erythematosus. Figures 1-3 respectively describe the pooled prevalence of autoantibodies, the pooled frequency of cumulative drug use and  the pooled mortality rate in Native sub-Saharan Africans with systemic lupus erythematosus.

2. Experimental Design, Materials, and Methods
   • Searched databases and search strategy

A comprehensive search of PubMed, Excerpta Medica database (EMBASE), Web of Science, African Journals Online, and Global Index Medicus was conducted to identify all relevant articles published from January 1^st, 2008 to October 7^th, 2018, without any language restriction. We considered recent studies to have current and updated clinical overview in the region. We conceived and applied a search strategy based on the combination of relevant terms. The main search strategy in PubMed is shown in Table 4. This search strategy was adapted for the search in other databases. A manual search that consists of scanning reference lists of eligible studies and relevant reviews was performed to identify any studies missed during the review process or by the search strategy.

The titles and abstracts of the retrieved papers were independently screened by two investigators (ME and JRN) and the full-texts of papers deemed potentially eligible were further assessed for final inclusion. All discrepancies for study selection were resolved through discussion or with the arbitrage of a third investigator.

• Criteria for considering studies for the review
  • Types of studies

Observational studies including cross-sectional, case-control and cohort studies, as well as case series. We did not consider case reports, commentaries, letters to the editor and review articles.

• Types of participants

We considered studies involving African Black people (or multiethnic groups with possibility to extract information for the African Black people) living in sub-Saharan Africa regardless of the age and gender. Studies were excluded if: (1) they included multi-ethnic groups with no possibility to extract information for the African Black people exclusively (2) they included only a specific group of lupus patients e.g. lupus nephritis, neuropsychitaric lupus, cutaneous lupus, lupus pericarditis, lupus myocarditis, lupus in pregnant women (3) they included patients with overlapping syndromes.

• Condition

The diagnosis of systemic lupus erythematosus met either the 1982 American College of Rheumatology criteria [1], or the revised 1997 American College of Rheumatology criteria [2], or both.

• Outcomes of interest

The following outcomes were analysed: systemic lupus erythematosus prevalence; demographic, clinical and immunological characteristics of systemic lupus erythematosus; frequencies of cumulative drug use for the treatment of systemic lupus erythematosus and its complications; outcome measures of systemic lupus erythematosus.

• Data extraction and management

The data were extracted by two investigators (ME and JJB) using a preconceived, piloted and standardized data abstraction form. The following data were extracted and cross-checked to ensure that there was no missing information: name of the first author, year of publication, study design, period of recruitment of the study population, setting (country, unique/multiple site[s]), locality (urban/rural), sampling method, systemic lupus erythematosus diagnostic criteria and the outcomes of interest.

• Assessment of the methodological quality of studies

We used an adapted version of the tool developed by Hoy and colleagues to assess the methodological quality of included studies [3]. Three investigators (JJB, ME and FTAE) independently ran the assessment. Discrepancies were discussed and resolved by these investigators. Cohen’s κ statistics were used for inter-rater agreements between investigators regarding study inclusion and for the assessment of the methodological quality of all included studies.

• Data synthesis and analysis

The quantitative synthesis was done using the ‘meta’ packages of the R statistical software (version 3.5.1, The R Foundation for statistical computing, Vienna, Austria). We used the reference method for prevalence synthesis suggested by Barendregt and colleagues [4]. The prevalence of systemic lupus erythematosus and systemic lupus erythematosus autoantibodies, the frequencies of cumulative drug use and the mortality rate were recalculated based on crude numerators and denominators provided by individual studies. To minimize the effect of studies with extremely small or extremely large prevalence estimates on the overall estimate, the variance of study-specific prevalence was stabilized with the Freeman-Tukey double arcsine transformation before pooling the data with the random effects meta-analysis model [4]. Heterogeneity was assessed by the chi-square test on Cochrane’s Q statistic [5], and quantified by I² values. Low, moderate and high heterogeneity were considered for I² values ​​of 25%, 50% and 75% respectively [6]. The quality of all included studies and the risk of bias are presented in Table 5. The Egger’s test was used to assess the presence of publication bias [7]. A statistically significant publication bias was considered for p values < 0.1 [8]. We decided a priori that if we find publication bias, we will do no adjustment in regard, since we believed that the prevalence estimates of interest would likely be published even if they are substantially different from the previously reported estimates.

In total, 15 studies were included in the meta-analysis. Figure 4 describes the selection process.

The characteristics of the included studies [9-23] are displayed in Table 5 and the data provided here are linked to a systematic review and meta-analysis published in the Journal of Autoimmunity [24]