Capillary blood sampling: are the results comparable to venous sampling in health and disease

Lightbody, Tyrone Oliver (2017). Capillary blood sampling: are the results comparable to venous sampling in health and disease. University of Birmingham. M.Sc.

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Abstract

Background: Blood gas analyser (BGA) results are used to guide treatment, however their accuracy for some parameters is unknown. Blood tests taken from capillary blood can also be analysed by a BGA but again the accuracy is unknown.. Capillary and venous BGA tests were compared to gold standard tests for sodium, potassium, haemoglobin, glucose and lactate.

Methods: 23 healthy adults and 48 acutely unwell diabetic patients had ear lobe prick (EP) and finger prick (FP) (capillary) and standard venous blood samples. Venous samples went for standard laboratory (VL) reporting as well as being analysed in the BGA (VBG). Results were compared to international acceptability criteria. All studies had ethical approval (NRES14/WM/1057).

Results: VBG and EP sodium results met the acceptability criteria. FP samples marginally failed with 94.8% meeting the required level (95% within 4mmol/l of VL result). All potassium, haemoglobin and lactate samples failed to reach the required level of accuracy (95% within 0.5mmol/l, 5g/l and 0.5mmol/l respectively). Potassium FP and EP samples were more accurate than the VBG results (p<0.001). VBG glucose in the hyperglycaemic range met acceptability criteria (within 20% of VL) as did FP when values were >12mmol/l.

Conclusions: BGA results are sufficiently accurate for the analysis of sodium. FP and VBG glucose are suitable in hyperglycaemic ranges only. Capillary samples could be used as an alternative to VBG potassium if considering BGA measurement only. Results for other parameters should be used as a guide rather than as a definitive value.

Type of Work:

Thesis (Masters by Research > M.Sc.)

Award Type:

Masters by Research > M.Sc.

Supervisor(s):