Endocrine Abstracts

Background: Patients with hypoparathyroidism require frequent calcium measurements and currently there is no point of care device allowing this to be done at home by patients themselves. The aim of our study was to evaluate whether ionized calcium(iCa) can be accurately measured in venous and capillary blood and saliva by a repurposed device LAQUA.(R&D Ref 18/0058– IRAS 236079)

Methods: Patients undergoing thyroid and parathyroid surgery underwent daily measurements of venous blood adjusted calcium(adjCa, Roche-Cobas-Gen.2,) and ionized calcium (iCa, Blood Gas Analyser-ABL90) as “gold standard” and iCa in venous and capillary blood using LAQUA. Calcium was also measured in saliva in the main laboratory (Roche-Cobas-Gen.2) and LAQUA.

Results: 67 sets of measurements were obtained from 30 patients. We observed strong correlation between venous adjCa and BGA iCa. (r=0.95, P<0.001) with minimal average difference between measurements 0.03mmol/l (95%CI-0.11-0.05). Strong positive correlation was seen between BGA iCa and LAQUA iCa (r=0.75, P=<0.001) with average difference between measurements of 0.14mmol/l (95%CI:-0.11-0.41). A similar relationship was observed between venous BGA iCa and LAQUA capillary iCa(r=0.68, P=<0.001) with average difference of 0.22mmol/l (95%CI:-0.02-0.46). There was a positive correlation between saliva LAQUA iCa and saliva calcium Roche-Cobas-Gen.2 (r=0.76, P=<0.001) with average difference between measurements of -1.34mmol/l (95%CI:-3.67-0.99). No correlation between saliva calcium (Roche-Cobas-Gen.2) and blood adjCa(Roche-Cobas-Gen.2) was observed(r=0.17, P=0.2).

Conclusion: iCa could replace adjCa for monitoring hypocalcaemia and LAQUA is a promising device which might allow calcium measurements to be done at home by patients themselves.