Point-of-care glucose, ketone and urinalysis testing — branching viva

Branching viva — point-of-care glucose, ketone and urinalysis testing

The examiner releases the stem and then branches into four probes. A strong candidate names the test chemistry, defends the confirmation step, applies the ISPAD thresholds without prompting, and recognises the falsely reassuring results that this topic is built to prevent. ^{[6] [10]}

Opening (examiner)

"A five-year-old with known type 1 diabetes arrives vomiting and breathless. The bedside glucose meter reads 24 mmol per litre. Walk me through the point-of-care tests you would use and their limitations." ^[1]

Branch 1 — The glucose meter chemistry and the neonatal limitation (expected answer)

The capillary blood glucose meter measures the whole-blood glucose by the glucose oxidase or the glucose dehydrogenase electrochemical strip on the capillary sample, and it reports the result in five seconds in the millimoles per litre. The glucose oxidase reaction depends on the oxygen, which is the source of the oxygen interference, and the glucose dehydrogenase pyrroloquinoline-quinone variant cross-reacts with the galactose, the maltose, and the xylose. In the older child the meter is reliable, but in the neonate the high haematocrit, the variable oxygen, and the galactose or maltose interference bias the reading in either direction, so any critical or unexpected capillary glucose in a neonate is confirmed with the laboratory plasma glucose. ^{[6] [7]}

Probe. "The whole-blood glucose reads approximately ten to twelve per cent lower than the plasma glucose — why?" — The red cells contain less glucose than the plasma, so the whole-blood value sits below the plasma value, and the high neonatal haematocrit widens this bias. The device may report a whole-blood or a plasma-calibrated value, and the clinician must know which. ^[7]