Bone Abstracts

Background: Biochemical and haematological testing is recommended in the United Kingdom when non-accidental injury is suspected. We examined the associations of test results with radiologically-confirmed fracture(s), and between test results, in a retrospective observational cohort.

Methods: Infants up to age two years presenting with suspected non-accidental injury, without clinically-apparent bone disease, and where a skeletal survey was undertaken during the period 1st August 2013 to 31st July 2017, were included. Biochemical parameters: corrected calcium (cCa); phosphate (P); alkaline phosphatase (ALP) all measured by dry slide on the Ortho-Clinical Diagnostics Vitros 5·1 analyser; parathyroid hormone (PTH) by a CMIA method on the Abbott Architect i1000; 25-hydroxyvitamin D (25D) by liquid chromatography tandem mass spectrometry; and haematological parameters using a Siemens Advia 2120: haemoglobin (Hb); mean corpuscular haemoglobin (MCH); mean corpuscular haemoglobin content (MCHC); mean corpuscular volume (MCV); platelet count were collated together with the results of the radiological assessments. Radiographs were reported by experienced paediatric radiologists.

Results: Of 185 eligible infants (68 male), 67 (27 male) had one or more fractures. Mean PTH in the fracture and non-fracture groups was 51.1 and 31.6 ng/l respectively; difference 19.5 ng/l, 95%CI 0.7–38.3 ng/l, P=0.0420. The factors which in combination were most strongly associated with PTH were (in order of strength of association) ALP (positively), cCa (negatively), age (negatively), MCHC (negatively) and fracture (positively). The coefficient for fracture in the determination of PTH from the regression analysis (19.4 ng/l) was similar to the unadjusted analysis comparing the fracture and non-fracture groups. There was no clear association of PTH with timing in relation to fracture.

Conclusions: PTH was raised in infants who had fractured compared to those who had not; PTH was negatively correlated with MCHC suggesting a possible relationship of PTH with iron sufficiency. Further studies are needed to clarify the relationships of PTH, 25D and MCHC with fracture; it is unclear if PTH was increased before or after fracture occured. Interpretation of data from biochemical and haematological testing should be informed by the overall presentation in suspected non-accidental injury cases.

Disclosure: NJB consults for Alexion, Mereo, UCB and Amgen, and receives grant support for clinical studies from Alexion and Amgen.