Assessment of body composition in cystic fibrosis: agreement between skinfold measurement and densitometry

Introduction: few studies have evaluated body composition (BC) through different techniques, and the degree of agreement between them in adults with cystic fibrosis (CF). Objectives: to describe BC using techniques to assess nutritional status and to test their concordance in CF. Methods: a cross-sectional study in CF patients in a clinically stable situation. Nutritional assessment was performed using skinfold measurement (SM) and densitometry (DXA). Fat-free mass index (FFMI) was also determined. The diagnosis of malnutrition was established if body mass index (BMI) < 18.5 kg/m2. Fat-free mass (FFM) malnutrition was diagnosed when FFMI was < 17 kg/m2 in males and < 15 kg/m2 in females (FFMI: fat-free mass in kg/height in m2). Results: forty-one patients were studied (twenty-two females, 53.7 %); median age was 29.8 (interquartile range, 20.9-33.7); BMI was 21.6 (19.8-23.0). Only four (9.8 %) patients had a BMI < 18.5. By DXA, FFM (kg) results were: median, 52.8 (47.8-56.9) with FFMI of 17.9 (16.7-19.3) in males and 36.7 (33.1-38.9) in females, FFMI of 14.7 (14.2-15.8). Twenty (48.6 %) patients presented FFM malnutrition, with 16.7 % of males and 59.1 % of females being affected. By SM, the FFMI was 18.7 (17.2-20.0) in males and 14.9 (14.2-15.8) in females; moreover, sixteen (39.1 %) patients presented malnutrition of FFM, with 20.8 % of males and 61.8 % of females being affected. For FFM (kg), a high concordance was obtained between SM and DXA (intraclass correlation coefficient of 0.950); likewise when they were compared by applying the ESPEN criteria for FFM malnutrition. However, when the techniques were compared to classify malnutrition according to FFMI, the kappa coefficient was only moderate (k = 0.440). The mean difference between FFM by DXA and SM was +1.44 ± 0.62 kg in favor of SM, with greater dispersion as FFM increased. Conclusions: the prevalence of FFM malnutrition is high in adult CF patients, despite a normal BMI, especially in females. Notwithstanding the good statistical agreement between SM and DXA, concordance was moderate. Therefore, DXA remains the technique of choice, and SM may be used when the former is not available.