Lenka Turoňová, Miriam Čiljaková, Kristína Kubejová, Peter Bánovčin
Background: Demonstrate a false decrease in planar densitometric (DXA) parameters when compared to volumometric
bone mineral density (vBMD) in children with juvenile idiopathic arthritis (JIA) in relation to growth delay and present
of high disease activity as well as concomitant use of corticosteroid therapy.
File and Methods: 20 children with JIA Tanner stages 1-4 who were first DXA screened under conditions of high disease
activity prior to commencement of the biological treatment in comparison to the control group of healthy children of
the same age and gender (n=20) have been tested. In all listed Caucasian subjects planar and volumetric DXA parameters
in relation to height, sex, pubertal stage and selected characteristics of the underlying disease have been evaluated.
These parameters have been reconsidered after 2 years of biological treatment in order to assess the possible compensatory
growth spurt children with JIA in relation to disease activity decrease. Children no longer expected to grow
(ie, boys with JIA aged 17 years or older, Tanner stage V before the start of biological treatment and pubertal girls, Tanner
stage V, with onset of menarche 1 year before the onset of biologic therapy or girls with onset of menarche 2 years
before the onset of biological treatment) have been excluded.
Results: In the JIA group, when compared to healthy subjects, a significant reduction in body height (54.1 ± 24.1 percentile
in the control group vs. 46.3 ± 26.2 percentile in the JIA children group, p < 0.05) has been recorded. Similarly, in
all children with JIA statistically significant reduction in the level of planar DXA parameters when compared to healthy
controls (BMD L2-L4 in healthy children 0.632 ± 0.09 g / cm2 vs. 0.201 ± 0.17 in the JIA group, p < 0.005) has been observed.
Estimation of volumetric DXA parameters by mathematical calculations from data obtained both, the postero
terior (PA) scan as well as the combination of PA and lateral DXA scans of the lumbar spine (L2-L4 region), has been
evaluated. In summary, the DXA volume parameters in the investigated file of children with JIA were comparable to
the group of healthy children, and the values did not statistically significantly differ from healthy controls in any of the
Tanner 1-4 pubertal stages. The actual reduction in vBMD was observed in subjects with JIA in five cases (25%) only. After
one year of biological treatment duration a compensatory growth spurt accompanied by full normalization of planar
DXA parameters in most children with JIA was observed as these were heavily dependent on body height.
Conclusion: Children with chronic illnesses, delayed skeletal maturation, and delayed growth often have falsely diminished
DXA parameters when compared to healthy peers. This phenomenon occurs even if such a lower child is converted
to a volume ideally mineralized. By estimation of volumetric DXA parameters, this false drop can be to a high degree
corrected. At the same time, it is necessary to note that the rapid decline in JIA activity in relation to the early onset of
biological treatment is associated with growth spurt in growing children.