Prevalence of scleroderma in Spain: an approach for estimating rare disease prevalence using a disease model

To estimate scleroderma prevalence in Spain.

As no data were available for Spain we used reported scleroderma incidence (Silman's study on UK and Alamanos' on Greece), scleroderma cause-specific mortality, obtained through the National Institute of Statistics (codes included in M34 of the International Classification of Diseases, 10th revision) in Spain and remission data. Estimates were applied to the Spanish population and to all-cause mortality for 2004, broken down by age group and gender. Estimators were assumed to follow a Poisson distribution. DisMod-II software was used for this purpose.

Estimated prevalence was 0.23 and 0.71 cases per 10,000 people for men and women, respectively, based on UK incidence, and 0.28 and 2.58 cases per 10,000 people, respectively, based on Greek incidence. Estimated age at disease onset ranged from 50 to 58 years among men and from 52 to 55 among women, according to UK and Greek data, respectively. Mean duration of the disease was estimated to be in the range of 17-20 years for men and 19-20 for women.

DisMod-II is useful for obtaining, modelling and confirming variability ranges of prevalence found in literature. It also provides information for orphan drug designation and for supporting public health decisions regarding rare diseases.