Most useful investigation in diagnosis of diabetic ketoacidosis –
**Core Concept**
Diabetic ketoacidosis (DKA) is a serious complication of diabetes characterized by hyperglycemia, metabolic acidosis, and ketosis. The diagnosis of DKA relies on a combination of clinical evaluation, laboratory tests, and imaging studies.
**Why the Correct Answer is Right**
The most useful investigation in diagnosing DKA is the **arterial blood gas (ABG) analysis**, which provides information on the level of acidity in the blood. In DKA, the blood pH is typically below 7.3, and the bicarbonate level is low. The ABG analysis also helps to identify the presence of ketosis, which is a hallmark of DKA. The ABG analysis can be performed quickly and provides valuable information that guides the management of DKA.
**Why Each Wrong Option is Incorrect**
**Option A:** Serum osmolality is not the most useful investigation in diagnosing DKA, although it can be used to assess the severity of hyperglycemia. Elevated serum osmolality is a common finding in DKA, but it does not provide information on the level of acidity or the presence of ketosis.
**Option B:** Urine ketone testing is a useful screening test for DKA, but it is not as sensitive or specific as ABG analysis. Urine ketone testing can be used to monitor the response to treatment, but it is not the most useful initial investigation.
**Option C:** Fasting blood glucose is an essential test for diagnosing DKA, but it does not provide information on the level of acidity or the presence of ketosis. Fasting blood glucose can be used to assess the severity of hyperglycemia, but it is not the most useful investigation in diagnosing DKA.
**Clinical Pearl / High-Yield Fact**
In patients with DKA, the presence of a **low bicarbonate level ( 12 mmol/L) on ABG analysis is highly suggestive of DKA. The anion gap is calculated by subtracting the sum of sodium and chloride from the bicarbonate level.
**Correct Answer:** A. Arterial blood gas (ABG) analysis.