The Epidemiology of Chronic Urticaria in Cape Town, South Africa: A Review of Two Tertiary Referral Centers

Abstract

There is a paucity of information on Chronic Urticaria (CU) in Africa and the global south [1]. We have conducted a retrospective folder review of the Cape Town UCARE centre (https://ga2len-ucare.com/)—the only one on the continent—and dermatology services of the only two tertiary hospitals in Cape Town, South Africa. All patients that were coded L50 (the ICD10 code for urticaria) were reviewed (see Figure S1) this study was approved by the University of Cape Town Human Research Ethics Committee (HREC 603/2023), and all patients provided informed consent for the use of photographs. This multicentre study is the largest cohort of Chronic Urticaria (CU) reported to date in Africa (n = 939)—and, despite limitations of missing data, it provides several valuable insights. The global prevalence of CU ranges from 1%–4.4% [2], with international tertiary dermatology and allergy clinics reporting CU prevalence rates of 1.3%–1.7% [3, 4]. In the Tygerberg Hospital Dermatology clinic, CU accounted for 0.6% of patients, while at Groote Schuur Hospital Allergy/Dermatology clinics, CU accounted for 1.8% of patients (see Figure S1). Our population is multiethnic, with 85.8% (806/939) having darker Fitzpatrick skin tones (III-VI). Given the underrepresentation of darker skin tones in dermatology/allergy literature [5] Figure 1 provides a collection of photographs showing morphologies of chronic urticaria against the background of darker skin. The CIndU group had a higher prevalence of Fitzpatrick I-II (paler skin) while the angioedema without urticaria group had a high prevalence of Fitzpatrick V-VI (darker skin tones) (p < 0.001) (see Table 1). Chronic Spontaneous Urticaria (CSU) without Chronic Inducible Urticaria (CIndU) was commonest (81% [761/939]), with 8.6% (81/939) having combined CSU/CIndU. Isolated CIndU was found in less than 5% (42/939), with heat and delayed pressure urticaria being the most common; symptomatic dermatographism (n = 19) and cholinergic urticarias (n = 9) were rare. Only 2.2% (21/939) had recurrent angioedema without urticaria.

Clinical characteristics, associated co-morbidities, and exacerbating factors from our cohort were all similar to other reported CU cohorts from different regions (Table 1, Tables S1 and S3) [2]. CU with associated angioedema typically has a more severe course [6], and our cohort showed a 65% rate of associated angioedema, which is higher than global averages [6]. Consistent with reports about Mast cell-isolated recurrent angioedema [6], this cohort of patients was older, had higher rates of food additive sensitivities, mental illness, hypertension and gastrointestinal symptoms than other CU groups (Table S1).

The use of Patient Reported Outcome Measures (PROMs) was poor (8.6%–14.9%) and restricted to UCARE centre patients. Similarly, less than a third of patients had endotyping or screening for co-morbid thyroid autoantibodies. However, of those endotyped, 237/293 (81%) had total IgE > 43ku/l and 34/266 (12.7%) had elevated anti-TPO antibodies (Table S2) supporting the predominance of autoallergy CSU and indicative that the spectrum of CU in South Africa is likely similar to other regions [2]. Despite a significant burden of severe disease (indicated by high co-morbid angioedema, and a median UAS7 of 21 [IQR 8; 32] in those reporting PROMs), only 46.3% of patients accessed high-dose antihistamines, and just 13 accessed third-line therapies (Table 1).

This study highlights that although the prevalence of severe CU may be lower than reported in other countries, there is a sizable burden of CU in South Africa. Our data from a diversity of ethnicities is likely generalisable to other African countries. Our data underscore the urgent need for greater awareness and better education around the use of PROMS even amongst specialist healthcare providers, for example, dermatologists and allergists. Greater awareness and increased use of PROMs is needed to guide appropriate treatment escalation. The huge access gap—due to cost—to highly effective biologics in even a middle-income country like South Africa, when compared to high-income countries, also needs attention and advocacy. Our recent review article on CU in Africa suggests there is a similar picture across the continent, meaning a huge unmet burden of disease with considerable impact on quality of life [1]. Innovative strategies to improve access to targeted therapies, as well as ongoing study of the use of alternative, more affordable treatments like methotrexate, dapsone, UVA and also auxiliary strategies such as pseudoallergen-free diets or stress control merit ongoing study [7]. Furthermore, while several novel therapies for CU enter international guidelines, industry, governments and academia need to work together to improve access for those suffering in low/middle-income countries.

J.P. developed the research concept. C.D., M.D., Y.J., Q.G.M., S.N., B.H., E.K., and N.A. conducted folder reviews and data entry. C.D. and L.M. did the statistical analysis. C.D. and J.P. wrote the manuscript. All authors reviewed and approved themanuscript.

Dr. Cascia Day has received funding for her PhD from the Discovery Foundation and the South African Medical Council Division of Research Capacity Development Programme. The degree from which this study emanated was funded by the South African Medical Research Council through its Division of Research Capacity Development under the Clinician Researcher Development Programme with funding received from the South African National Department of Health. The content hereof is the sole responsibility of the authors and does not necessarily represent the official views of the SAMRC or the funders. J Peter has received speaker's fees or honoraria from CSL Behring, Novartis, Sanofi Regeneron, and Takeda. He has received educational grants from Astria, Cipla, Glenmark Pharmaceuticals, Kalvista, Pharvaris, and Takeda. He serves on the advisory board of Astria and Pharvaris.