Original article
Prevalence of autosomal recessive congenital ichthyosis: A population-based study using the capture-recapture method in Spain

https://doi.org/10.1016/j.jaad.2011.07.033Get rights and content

Background

Previous reports on the prevalence of autosomal recessive congenital ichthyosis (ARCI) were based on single source data, such as lists of members in a patient association. These sources are likely to be incomplete.

Objectives

We sought to describe the prevalence of ARCI.

Methods

We obtained data from 3 incomplete sources (dermatology departments, a genetic testing laboratory, and the Spanish ichthyosis association) and combined them using the capture-recapture method.

Results

We identified 144 living patients with ARCI. Of these, 62.5% had classic lamellar ichthyosis and 30.6% had congenital ichthyosiform erythroderma. The age distribution included fewer elderly patients than expected. The prevalence of ARCI in patients younger than 10 years, the best estimate as less subject to bias, was 16.2 cases per million inhabitants (95% confidence interval 13.3–23.0). According to the capture-recapture model, 71% of the patients were not being followed up in reference units, 92% did not have a genetic diagnosis, and 78% were not members of the ichthyosis association.

Limitations

The prevalence of ARCI in Spain and findings related to the Spanish health care system might not be generalizable to other countries.

Conclusions

The prevalence of ARCI is higher than previously reported. Many patients are not being followed up in reference units, do not have a genetic diagnosis, and are not members of a patient association, indicating room for improvement in their care. Data suggesting a reduced number of older patients might imply a shorter life expectancy and this requires further study.

Section snippets

Methods

This was a prospective, population-based, cross-sectional study. The study protocol was approved by the Comité Etico de Investigación Clínica de Galicia (2010/445), and by the ASIC.

Lists of patients with ARCI were obtained from 3 sources: dermatology departments acting as reference centers, the reference center for genetic diagnosis of the disease, and the ASIC (including members of the association and other affected individuals of whom they were aware). All provided a list of patients with

Results

We identified 144 patients with ARCI. Of these, 21 were present in two sources, and 4 in 3. A table showing the overlap of the data sources is available from the corresponding author. Diagnoses are described in Table I. Age distribution of patients was compared with the age distribution of the Spanish population (Fig 1).

The capture-recapture method generates several models to fit the relationship between the different data sources. In our study, all models gave very similar estimates, which is

Discussion

Estimates of the prevalence of ARCI in the Spanish population ranged from 7.2 to 16.2 cases per million, depending on the age group. We also showed that individual data sources were incomplete, so the use of the capture-recapture technique was justified to improve the estimation.

Assumptions of the capture-recapture method are: (1) a closed population (not affected by migration), (2) correct identification of subjects and overlap between the different data sources, and (3) the probability of

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Funding sources: None.

Conflicts of interest: None declared.

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