The clinical features that contribute to poor bone health in young Australians living with cystic fibrosis: A recommendation for BMD screening

Abstract

Background For Australians living with cystic fibrosis (CF), increased longevity means greater consideration needs to be given to long‐term endocrine sequelae such as CF‐related bone disease. Deficits in bone mass accrual are most likely to occur during childhood and adolescence. Current guidelines in Australia suggest repeat dual‐energy X‐ray absorptiometry (DXA) scans every 2 years. This study aims to stratify clinical factors that determine future bone health in the Australian CF population and use this to guide a more streamlined approach to bone health screening. Methods This study was a retrospective audit of all patients diagnosed with CF who were treated at the Royal Children's Hospital Melbourne, Australia from 2000 to 2016 (n = 453). Two hundred and two patients had a DXA scan in the study period (191 with height‐adjusted data) and 111 patients had more than one scan (108 with height‐adjusted data). An investigation into the associations between bone mineral density (BMD) Z score and potential risk factors was conducted using DXA and historical data. Results The main predictor of future BMD was the previous BMD Z score (p < .001). Other factors found to be determinants of BMD included nutritional status, lung function (FEV1), age, history of previous fracture, oral corticosteroid use, and the number of hospital admissions. However, after adjusting for previous BMD, evidence of an association remained only with nutritional status, FEV1, and number of hospital admissions. Conclusion Second yearly scans may be unnecessary in children with an adequate DXA score on the initial scan who remain clinically stable. However, clinical deterioration in those whose BMD was previously normal, may require closer monitoring of bone health. We propose a guideline for the frequency of DXA monitoring in relation to clinical risk factors.

Dilemmas in the Management of Osteoporosis in Younger Adults

“…YAs with cystic fibrosis (CF) have higher risk of fracture, secondary to malabsorption of calcium and vitamin D, ( 76 ) lower body weight, ( 77 ) delayed puberty, ( 77 ) GIO, ( 77 ) poor nutrition, ( 78 ) limited physical function, ( 79 ) chronic inflammation, and underlying impact of the CF transmembrane conductance regular (CFTR) gene mutation. ( 80 ) Up to 52% of YAs with CF may have associated bone disease, ( 81 , 82 ) with a higher prevalence noted in cohorts of patients with end‐stage lung disease.…”

An update on methods for assessing bone quality and health in Cystic fibrosis

“…Height for age Z-score (HAZ) adjustment of aBMD, accounting for variability in growth and puberty, has been found to be a better approach to minimize the effect of stature on mineralization [34] . In a recently published study of children with CF, baseline HAZ adjusted DXA Z-scores correlated strongly with future bone density [25] , indicating that only certain patients may need more frequent bone health screening. Routine DXA reports will not include these adjustment results; however, online calculators are available to adjust aBMD and BMC for HAZ in children and young adults ( https://zscore.research.chop.edu/calcpedbonedens.php ) [35] .…”

“…aBMD and BMC for the total body is presented as the total body less head (TBLH) in order to subtract the mineral contribution of the larger cranium in young children. The non-linear nature of bone mineral accrual in childhood and adolescence necessitates reference data for comparison across age, sex, pubertal status, and ethnicity [24] , [25] . The Bone Mineral Density in Childhood Study (BMDCS) is a multicenter national study with the purpose of creating sex and puberty specific normative aBMD and BMC data for children, adolescents, and young adults.…”

Cystic Fibrosis Bone Disease: The Interplay between CFTR Dysfunction and Chronic Inflammation

“…Indeed, children with cystic fibrosis already have bone alterations [ 54 , 55 , 56 , 57 , 58 ] which increase with age [ 59 ]. The progressive bone loss [ 48 ] in cystic fibrosis patients correlates with reduced lung function [ 60 , 61 , 62 ], recurrent pulmonary exacerbations [ 63 ], inflammation [ 64 ] and reduced muscle strength [ 65 ]. Yet, these correlations and a reduced bone mineral density are not always identified in all cystic fibrosis populations [ 45 ], suggesting that other factors may also play a role in the development of bone loss in these patients [ 66 ].…”