Most Appropriate Initial Diagnostic Test
Check the blood glucose immediately with a point-of-care glucometer. 1
Rationale for Immediate Glucose Testing
In a confused elderly diabetic patient presenting to the ED, hypoglycemia is a life-threatening emergency that must be ruled out first before pursuing other diagnostic workup. 1 The clinical presentation of confusion in a diabetic patient, particularly with the associated hypothermia (35.5°C), is highly suggestive of hypoglycemia, which can present with hypothermia as its only sign. 1
Why Glucose is the Priority
Hypoglycemia is immediately reversible and life-threatening - In insulin-dependent diabetics, hypoglycemic encephalopathy with hypothermia is a critical condition requiring immediate diagnosis and treatment. 1
Altered mental status in diabetics demands glucose assessment first - Confusion represents a classic symptom of hyperglycemia or hypoglycemia, and a random plasma glucose ≥200 mg/dL with classic symptoms of hyperglycemia confirms diabetes-related crisis. 2
The hypothermia is a critical clue - Subnormal temperature (35.5°C in this case) is a specific indicator of hypoglycemia and may be the only presenting sign. 1
Why Other Tests Are Not Initial Priority
CT head (Option B) - While important to rule out stroke or intracranial pathology in confused patients, it should not precede glucose testing in a diabetic patient, as hypoglycemia is immediately treatable and can mimic stroke. 1
Ammonia (Option A) - Hepatic encephalopathy is less likely without other signs of liver disease, and glucose abnormalities are far more common in diabetic patients presenting with confusion. 1
TSH (Option D) - Hypothyroidism can cause hypothermia and confusion, but this develops over weeks to months, not acutely over two hours as described in this case. 1
Clinical Approach
The correct answer is C: glucose testing should be performed immediately at the bedside. 1 This can be done with point-of-care glucometry while other assessments proceed, and if abnormal, should be confirmed with laboratory plasma glucose measurement. 3, 4
Common Pitfall to Avoid
Do not delay glucose testing to pursue neuroimaging or other diagnostic studies in a diabetic patient with acute confusion. 1 The combination of confusion and hypothermia in a diabetic patient is hypoglycemia until proven otherwise, and delayed recognition can result in permanent neurological damage or death. 1