Comparison of self-reported and measured height and weight in patients with psoriasis

Excerpt

Self-reported weight and height are usually collected during the clinical examination. However, these measures are often misreported [1]. Height and weight are the two components of the body mass index (BMI, kg/m²). A high BMI (which indicates overweight or obesity) is associated with an increased risk for many serious diseases and health conditions and even with overall and cause-specific mortality. There is evidence that obesity is associated with psoriasis, both predisposing to the development of the disease and exacerbating it [2], and even influencing the treatment outcome. The objective of our cross-sectional, observational study was to investigate the presence of possible biases in self-reported height and weight measurements in patients with psoriasis. Consecutive individuals with psoriasis with both self-reported and measured weight, height, and BMI were 2720, 2665, and 2645, respectively. Overall, the values of the self-reported weight were lower than the measured weight with a mean difference greater than − 1 kg (Table 1). The magnitude of weight underestimation was higher for females and it increased with the increasing value of measured weight. The Bland and Altman 95% confidence interval (CI) of the limits of agreement (LOA), which provides an indication of the extent of under- or over-estimation of the self-reported values when compared to measured values, was − 8.2 kg, + 5.8 kg. The values of the self-reported height were overall higher than the measured height, with a mean difference of almost + 2 cm (Table 1). This overestimation was larger in females, it increased with age, and decreased with greater values of the measured height. The Bland–Altman 95% CI of the LOA was − 4.4 cm, + 8.2 cm. Such differences resulted in an underestimation of the self-reported BMI in comparison to measured BMI with a mean difference of 1 point (95% CI of the LOA: − 4.6 kg/m², + 2.4 kg/m²). This underestimation was larger in females, it increased with age and with greater measured weight, while it decreased with increasing value of measured height. Kappa coefficient for BMI categories was 0.71 (95% CI 0.69, 0.72) representing substantial agreement (Table 2). However, using self-reported BMI, 24.6% of overweight patients were categorised as normal weight, while 26.4% of obese patients were classified as overweight. This means that approximately ¼ of obese or overweight participants were misclassified. Our findings are consistent with the results of other studies [3, 4]. Observed discrepancies may be due to the need to adhere to socially desirable aesthetic standards. Moreover, weight-related stigma experiences appear to be more frequent in women than in men, and increase with weight [5]. Self-report bias has significant consequences for the accuracy of a screen for overweight and obesity. Misclassification may have important consequences when assigning patients to treatment groups in clinical trials. To the best of our knowledge, this is the first study comparing self-reported and measured height and weight in patients with psoriasis. In conclusion, it is crucial to have accurate measures of BMI, in particular within the framework of clinical trials, when studying the effect of treatment in different groups of patients. …