A 9 year old boy presents with glycosuria after an appendectomy but has no history of diabetes. What is the most appropriate follow-up investigation?

The most appropriate follow-up investigation in this scenario is fasting blood glucose. This test is crucial in evaluating the possibility of diabetes mellitus, particularly since the child has presented with glycosuria, which means that glucose is present in the urine. In the absence of a known history of diabetes, assessing fasting blood glucose levels can provide essential information regarding the child's glucose metabolism and whether there is a need for further investigation or intervention.

When fasting blood glucose levels are measured, they provide a snapshot of how well the body is managing glucose without the influence of recent food intake. In children, like adults, a fasting blood glucose level of 126 mg/dL or higher is indicative of diabetes. Additionally, if an abnormal result is found, it may warrant further testing, such as an oral glucose tolerance test, to confirm a diagnosis.

Other investigations such as glycated hemoglobin (HbA1c) are useful for assessing long-term glucose control and may not be as reliable in the acute context following the child's appendectomy. Similarly, while random blood glucose could be informative, fasting levels are preferred when assessing for diabetes, especially since the presence of glycosuria suggests that further evaluation of blood glucose is necessary. The 24-hour urine cortisol test pertains more to adrenal function