Having been approached by the British Paediatric and Adolescent Bone Group (BPABG) in relation to making some amendments to the timing of blood investigations for fractures, Chapter 9: Recognition of Physical Abuse of the Child Protection Companion has been revised.
Currently, measurement of parathyroid hormone (PTH) is recommended by the Child Protection Companion when a fracture is found. Given that fractures are frequently only found following skeletal survey done to investigate a suspected inflicted injury, this often means the child has to re-attend and be consented for a further blood test.
The difficulty in interpreting PTH in this context is compounded due to a number of reasons:
- Normal reference range in healthy infants can vary significantly
- Vitamin D supplementation may have an impact even where serum vitamin D concentration falls within the ‘sufficient range’
- Without good data on what healthy looks like it is even harder to be clear about the impact of a fracture on PTH levels, and
- In suspected inflicted injury there is often no clear history of the timing of the fracture(s)
The BPABG has responded to these challenges by recommending that PTH should be measured when the first set of blood samples is taken, close to the time of the initial skeletal survey. This more consistent approach will enable paediatricians to more easily interpret the data provided by biochemical testing and prevent the need for further needle insertion should a fracture be revealed either by the initial or the follow-up skeletal survey. Interpretation must be made in the context of both the clinical history and consideration of the other available biochemical data. It is hoped that over time, a consistent approach across the UK, will improve our understanding and interpretation of PTH results in the context of child protection investigations.
What will this mean for my practice?
These changes will result in a slight change of practice, with the recommendation to consent for and request calcium, phosphate, alkaline phosphatase, vitamin D and parathyroid hormone in all children at the point of decision to do a skeletal survey rather than once a fracture is confirmed. This will usually require sending an additional bottle, when the blood tests for bruising are performed.
It is advisable to contact your local laboratory, or consult local guidelines, with regard to sample tube type as while an ethylenediaminetetraacetic acid (EDTA) tubes can be used for PTH some laboratories use lithium heparin bottles. It is equally important to enquire about what volume of blood is required to avoid an "insufficient sample" report.
This may result in abnormal findings in children who subsequently are not found to have fractures, which may then need further need further investigation, treatment or discussion to interpret the relevance of the abnormal result. We hope that this consistent approach will over time improve our understanding and interpretation of these results in otherwise healthy children.