|
Indian Pediatr 2017;54: 973-974 |
|
Bone Mineral Density in Cystic Fibrosis: Few
Concerns: Author's Reply
|
Sumita Gupta and *SK Kabra
Department of Pediatrics, AIIMS, New Delhi, India.
Email: [email protected]
|
We are thankful to the author for his interest in our study [1]. The
concern regarding self-assessment of pubertal growth is well noted.
However, many children may not consent for detailed examination, and
self-assessment may be acceptable [2]. It may be possible that few of
the subjects may have not interpreted their pubertal stage correctly,
but the influence of this misinterpretation was assumed to have
influenced both the groups equally.
Physical activity level was estimated using HAES only
for Cystic fibrosis patients. Several factors such as nutrition,
pulmonary function, physical activity, puberty and glucocorticoids
affect bone mineral density (BMD) in patients. Therefore, lower physical
activity may only be a partly contributing for the difference in BMD and
bone mineral apparent density (BMAD) of the two groups.
Due to word limit in main manuscript we were unable
to provide details of measuring BMD and BMAD. DXA scan (Hologic QDR
4500A, Hologic Inc., Bedford, MA, USA) was performed of whole body using
standard positioning techniques (as mentioned in the manufacturers
manual). The measurements taken were: (i) Whole body bone mineral
content (in g); (ii) Whole body bone mineral area (in cm 2);
(iii) Whole body bone mineral density (in g/cm2).
BMAD was calculated for lumbar spine and whole body using the methods
suggested by Katzman, et al. [3]. Quality control procedure,
which included whole body (Hologic WB # 1252) phantom scanning before
subject evaluation, was completed prior to testing on each testing day
and it remained stable during the entire study period. In addition to
this, short term precision error for the DXA scans was calculated by
triplicate measurement of 15 healthy subjects as per the method
suggested by Glûer, et al. [4]. Re-positioning of the subjects
was done between measurement and single trained technician performed and
analyzed all the scans to avoid inter-personnel variations; the person
was blinded to the subject’s group (Cystic fibrosis/Control). The
calculated coefficient of variation of whole body was 1.3% for BMD.
References
1. Gupta S, Mukherjee A, Khadgawat R, Kabra M, Lodha
R, Kabra SK. Bone mineral density of Indian children and adolescents
with Cystic fibrosis. Indian Pediatr. 2017; 54:545-9.
2. Marshall WA, Tanner JM. Variations in the pattern
of pubertal change in boys. Arch Dis Child. 1970;45:13-23.
3. Katzman DK, Bachrach LK, Carter DR, Marcus R.
Clinical and anthropometric correlates of bone mineral acquisition in
healthy adolescents girls. J Clin Endocrinol Metab. 1991;73:1332-9.
4. Glûer CC, Blake G, Lu Y, Blunt BA, Jergas M, Genant HK. Accurate
assessment of precision errors: How to measure the reproducibility of
bone densitometry techniques. Osteoporos Int. 1995;5:262-70.
|
|
|
|