Endocrine Abstracts (2001) 2 P1

Routine biochemistry in patients at risk of osteomalacia in Bradford

SR Peacey

Department of Diabetes & Endocrinology, Bradford hospitals NHS Trust, Bradford, UK.

Vitamin D deficiency and osteomalacia continue to cause significant morbidity in Bradford. Outpatient attendance suggests this condition remains widespread. Poor awareness of this preventable and treatable condition exists. This audit was undertaken to highlight the frequency of normal biochemistry in patients with osteomalacia / vitamin D deficiency. Fifty-five patients (4M, 51F; 51 Asian, 4 Caucasian) were identified from our departmental computerised endocrine database. 25-hydroxyvitamin D (25OHD), parathyroid hormone (PTH), adjusted calcium (Ca), phosphate (PO4) and alkaline phosphatase (ALP) had been measured in all patients. All had hypovitaminosis D (<10 ng/l) and elevated PTH (>54 pg/l) - hypercalcaemic patients were excluded. Median (range) 25OHD 3.0 (1.3 - 9.3) ng/l, PTH 105 (55 - 1662) pg/l, Ca 2.20 (1.38 - 2.44) mmol/l, PO4 1.01 (0.45 - 1.55) mmol/l, ALP 281 (91 - 2863) IU/l. Despite low 25OHD and raised PTH in all patients, normal levels of calcium, PO4 and ALP were found in 64%, 80% and 31% patients respectively. Twenty-seven % patients had normal calcium, phosphate and ALP levels. Only 1/55 patients had abnormal PO4 in isolation. Those patients with normal Ca, PO4 and ALP (Nbio, n = 15) had significantly lower PTH; 91 (59 - 322) pg/l compared with those patients with one or more abnormal biochemical parameters (ANbio, n = 40); PTH 143 (55 - 1662) pg/l; p < 0.005. However, 25OHD levels were similar; Nbio 3.0 (1.5 - 7.3) ng/l vs ANbio 3.1 (1.3 - 9.3) ng/l; p = 0.81. Assuming elevated PTH levels in the context of 25OHD deficiency indicates underlying osteomalacia or risk of progressive bone damage; (i) measuring only routine biochemistry (Ca, PO4, ALP) misses 27% of patients at risk, (ii) 25OHD levels do not indicate the severity of bone disease, (iii) PO4 is a very poor indicator of bone disease, (iv) PTH should be measured in all patients with low 25OHD.

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