If the KH is not investigated during a spontaneous acute episode with severe symptoms and signs, a controlled fasting test in the hospital setting can help to establish the KH diagnosis and to give an impression of its severity. Dependent on age, an overnight fasting study can be performed until the glucose is either < 50 mg/dl (2.8 mmol/L) or the BOHB is > 2 mmol/L. At the end of the fasting study, a diagnostic critical sample is obtained. A controlled fasting study with frequent monitoring of both glucose and BOHB allows the physician to identify when the BOHB rises above 1 mmol/L and thus gives the family an understanding of the child’s fasting tolerance. Permanent or excessive ketosis should lead to investigations for ketone transporter or utilization defects.
Determining the frequency and severity
Once the diagnosis of IKH is established, the frequency and severity of KH should be determined as part of the initial workup. Home monitoring with point of care (POC) meters with testing for glucose and ketones should be performed, particularly on waking in the morning or with symptoms until a true pattern emerges. CGM may be helpful, but are not rigorously studied in IKH and cannot stand alone due to inaccuracy at lower glucose levels. The episodical nature of KH may call for prolonged home monitoring in pathological KH.
A diagnostic challenge
Patients with pathological KH represent a diagnostic challenge to physicians and caretakers. Pathological KH with or without atypical manifestations should lead to expanded diagnostic procedures.