The rationale for office testing rests on the need for rapid turnaround of results so therapeutic intervention may be made in real time. It is hoped that prompt intervention will prevent more serious complications that would necessitate treatment at a more complex site at a later date. Another rationale for office testing is the convenience of the patient who does not have to travel to another site for testing. This must be balanced against the expense of increased regulation, reimbursement rates, and liability issues. The most common chemical test performed in the office laboratory is serum or whole blood glucose.
Most methods employ one of two enzymes for measurement, either glucose oxidase or hexokinase.
Urine glucose testing, while non-invasive, is not considered helpful because the renal threshold at which blood glucose spills into urine varies considerably from person to person. Patients with very elevated white counts will often display low glucose values due to increased cellular metabolism in the sample tube. Pregnant females usually have lower blood glucose values than non-pregnant females. The criteria for an abnormal glucose tolerance test to diagnose gestational diabetes takes this into account. The test strips for measuring glucose contain a measuring pad mounted on a solid support strip.