Which two findings are most informative for detecting isopropanol exposure?

• A. Serum osmolality and urine acetone
• B. Urine osmolality and serum osmolality
• C. Urine acetone and urine osmolality
• D. Serum sodium and serum acetone

Answer: (A)

Detecting isopropanol exposure hinges on two signals: an elevated serum osmolality caused by the alcohol itself, and the presence of acetone, its primary metabolite, in urine. Isopropanol is rapidly absorbed and raises the serum osmolality, creating an osmolar gap. As it is metabolized, acetone appears in the body and is excreted in urine, making urine acetone a useful, more specific marker for this exposure. Combining a high serum osmolality with detectable urine acetone provides both a general indication of recent alcohol ingestion and specific confirmation that the alcohol involved is isopropanol. Urine osmolality alone is less specific, serum sodium isn’t informative for this exposure, and urine acetone without the osmolality context doesn’t convey the immediacy of exposure as clearly.