Tyrone Oliver Lightbody, Peter Nightingale, Vinay Reddy-Kolanu and Elizabeth Sapey
Diabetic emergencies are associated with derangements in glucose and electrolytes with guidelines supporting treatment and serial monitoring. In clinical practice this is often achieved using a venous blood sample assessed using a blood gas analyzer (BGA), however their accuracy in measuring glucose, potassium and sodium in acutely unwell adults is unknown. Capillary blood tests can measure these parameters using a BGA and may be more acceptable to patients. We compared capillary and venous BGA results to gold standard venous laboratory sodium, potassium and glucose in acutely unwell diabetic patients and healthy controls to determine their accuracy and acceptability.
Methods: 48 acutely unwell diabetic patients and 23 healthy adults had consecutive bloods taken from arterialized ear lobe (EP) and finger prick (FP) (capillary bloods) and a standard venous sample. Venous samples were sent to an accredited NHS hospital biochemistry laboratory (VL) for reporting as well as being analyzed in a BGA (VBG). Results were compared to internationally agreed acceptability criteria using Bland-Altman limits of agreements. Patient preferences were recorded.
Results: VBG glucose met acceptability criteria (results within 20% of VL result) as did FP glucose when glucose values were ≥ 11.2 mmol/l but not when results were within the normoglycaemic range. Venous and capillary BGA potassium did not meet acceptability criteria (within 0.5 mmol/l of VL result) although capillary samples were more accurate than the VBG results (p<0.001). FP, EP and VBG sodium all met acceptability criteria (>95% within 4 mmol/l of VL result). Participants found capillary tests less painful (p<0.001) and preferred FP testing method to serial venous blood tests (p=0.002).
Conclusion: Capillary and VBG samples can be used to guide acutely unwell diabetic patient treatment (with capillary testing preferred by patients) but caution is required as there is deviation from laboratory results, for potassium particularly.
Ethical approval was provided by NRES West Midlands (14/WM/1057).