The excess burden of trachomatous trichiasis in women: a systematic review and meta-analysis

Methodological quality of the review: Low confidence

Author: Cromwell EA, Courtright P, King JD, Rotondo LA, Ngondi J, Emerson PM

Geographical coverage: Africa, Asia, Middle East and South America

Sector: Trachoma

Sub-sector: Prevelance surveys

Equity focus: Women

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

It is widely accepted that women carry an increased burden of trachomatous trichiasis compared with men, but there is no systematic review of the available prevalence surveys in the peer-reviewed literature.

Objectives:

To identify population-based trachoma prevalence surveys utilising the World Health Organisation (WHO) simplified grading system that includes data for trichiasis.

Main findings:

24 studies met the inclusion criteria. The studies were conducted in 12 countries between 1989 and 2008 including Brazil, Egypt, The Gambia, Ghana, Morocco, Myanmar, Nigeria, Oman, Sudan, Tanzania, Ethiopia and Vietnam. 23 were published in English and one in French.

The overall odds of trichiasis in women compared with men was 1.82 (95% CI 1.61—2.07). Individual survey odds ratio (OR) ranged from 0.83 (95% CI 0.40—1.73) in Myanmar to 3.82 (95% CI 2.36—6.19) in Ethiopia. Findings suggested that there were statistically significant differences in odds of trichiasis by gender in 17 of the 24 studies, all of which showed increased odds of trichiasis in women compared with men.

Authors noted that this data confirmed the perception that women have a greater burden of trichiasis, and that this burden persists across all populations studied. Authors suggested that women must be specifically and deliberately targeted for trichiasis surgery if the aim of eliminating blindness from trachoma is to be achieved.

Methodology:

Authors conducted a search on PUBMED, MEDLINE, OVID and Cochrane for relevant studies. The reference lists of retrieved articles were hand-searched to identify other studies that may have qualified for inclusion in the review. Studies were included if they met the following criteria:

• They were published in a peer-reviewed journal
• They used population-based sampling methodology to determine the prevalence of trichiasis
• They used the WHO simplified grading system
• The survey reported either sex-specific trichiasis prevalence or provided sufficient information to allow back-calculation of the number of TT cases (numerator) and the number of people screened (denominator) for both sexes.

Only population-based prevalence surveys were considered for inclusion since they provide a prevalence estimate applicable to the population from which the random sample was taken.

Applicability/external validity:

Authors state that the odds of developing trichiasis are higher for woman than men irrespective of their country of residence.

Geographic focus:

A sub-analysis of the 20 African studies (five of which were from Ethiopia) showed a summary of 1.90. Authors noted that these results should not be interpreted to mean the risk greater from African woman compared with woman in any other non-African endemic country.

Summary of quality assessment:

Overall, there is low confidence in the conclusions about the effects of this study as important limitations were identified. Authors did not conduct a comprehensive search of the literature, so we cannot be confident that relevant studies were not omitted in the review. Studies written in English and French only were included in the review and contacting authors/experts and searching grey literature was not part of the search strategy. Methods used to screen studies for inclusions and to extract data of included studies were not reported. In addition, authors did assess the risk of bias of studies, as such it is not clear which studies are subject to high or low risk of bias.