Testing for Vitamin D in High-Risk COPD in Outpatient Clinics in Spain: A Cross-Sectional Analysis of the VITADEPOC Study

Abstract

Background: Vitamin D deficiency has been associated with an accelerated deterioration in lung function and increased exacerbations in chronic obstructive pulmonary disease (COPD). 25(OH) vitamin D levels have been indicated as a potentially useful marker for adverse results related to COPD. Methods: VITADEPOC is a cross-sectional clinical study recruiting consecutive patients with high-risk COPD. The objective of our study was to investigate vitamin D determination frequency in patients with high-risk COPD in clinical practice at outpatient clinics in Spain and to describe the factors associated with vitamin D testing. We also aimed to determine the frequency of vitamin D deficiency in these patients. Results: Only 51 (44%) patients underwent vitamin D determination and 33 (28.4%) had received vitamin D supplements in clinical practice. The patients who underwent testing for vitamin D in clinical practice were more often women (58.8% vs. 26.2%, p < 0.001) with comorbidities such as osteoporosis (19.6% vs. 6.2%, p < 0.001) or chronic renal failure (7.8% vs. 0%, p < 0.001) and with exacerbator phenotype (55% vs. 32.3%, p = 0.015). A total of 63 (54.3%) patients had serum vitamin D levels <20 ng/mL at the inclusion visit. Of these, 29 (46%) had serum vitamin D levels <12 ng/mL (severe deficiency). Having a history of inhaled corticosteroids (OR 3.210, p < 0.016), being treated with a cycle of systemic corticosteroids (OR 2.149, p < 0.002), and having a lower physical activity level (OR 3.840, p < 0.004) showed a statistically significant positive association with vitamin D deficiency. Conclusion: The testing of vitamin D levels in patients with high-risk COPD treated at outpatient respiratory clinics in Spain is infrequent. However, when tested, a severe deficiency is detected in one in four patients. Efforts to optimize case detection in COPD are needed.

Keywords: adherence to recommendation; chronic obstructive pulmonary disease (COPD); high risk; testing for vitamin D; vitamin D deficiency.

Figure 1

Sampling process as described in a STROBE flow chart.

Figure 2

Characteristics of patients with COPD according to presence/absence of serum vitamin D level testing to detect vitamin D deficiency during follow-up in clinical practice. Note: Data are presented as mean (SD), number (%), or median (IQR). Abbreviations: IQR: interquartile range; BMI: body mass index; mMRC: modified Medical Research Council; MET: metabolic equivalent of task; FEV1: forced expiratory volume in 1 s; GesEPOC: Spanish National Guideline for COPD. * p < 0.001; α p < 0.05.

Figure 3

Relationship between low, medium, and high activity levels and vitamin D levels in COPD. ○ Outliers values: values more than 1.5 box lengths (IQR) away from the 25th and 75th percentile. * Extreme values: values more than 3 box lengths (IQR) away from the 25th and 75th percentile.

Figure 4

Relationship between number of cycles of systemic corticosteroids in the previous 6 months and vitamin D levels in COPD. ● Each dot on the scatterplot represents one observation from a data set. The position of the dot on the scatterplot represents its X and Y values.