Variation in reported prevalences of XXXX in The Netherlands: the impact of methodological variables.

@entity1 @entity101
STUDY OBJECTIVE: To estimate the prevalence of @entity101 in The Netherlands and to quantify the influence of methodological variables on the reported prevalences. DESIGN: A pooled analysis was performed based on reported age specific prevalences of @entity101 . A logistic model was used to estimate the probability of @entity101 . MAIN RESULTS: The age standardised prevalence of @entity101 varies more than fivefold between studies carried out in The Netherlands. The probability of having @entity101 was lower if blood pressure was measured at more than one point in time (Odds ratio 0.44 (OR) (95% confidence interval (95% CI) 0.38, 0.51) for @entity1 and 0.47 (0.41, 0.54) for @entity1 , and if the study was carried out more recently (OR 0.92 (0.91, 0.93) per year). The probability was higher if the study was carried out in a general practice (OR 1.14 (1.03, 1.27) for @entity1 and 1.52 (1.36, 1.69) for @entity1 ). The inclusion of treated @entity1 as @entity101 yields contradictory results for @entity1 and @entity1 . CONCLUSIONS: The strong variation in prevalence is explained by methodology and by a period effect indicating a decrease of the prevalence of @entity101 over time. Whether this decrease is true or caused by confounding due to unknown or unreported methodological variation over time is unknown. For future studies, a standardised method could reduce the influence of methodological variables and thereby the variation in reported prevalences.
