Stability of lactic acid in cerebrospinal fluid specimens.

The stability of lactic acid in cerebrospinal fluid specimens from children with or without infections of the central nervous system was determined. Twenty-six patients were studied. These were ten children with bacterial meningitis, nine with aseptic meningitis and seven without any inflammation of the central nervous system. The specimens were left at room temperature and lactic acid concentration was measured at sequential intervals: 15 minutes, and two, six and 24 hours following their collection. A decline in the concentration was noticed in all specimens. However, the most marked total reduction in lactic acid concentration was noted in specimens obtained from patients with bacterial meningitis. The average reduction in that group was 5 mg/dl after two hours, 11 mg/dl after six hours and 18 mg/dl following 24 hours. Lactic acid concentration remained unchanged up to 72 hours in specimens frozen at -20 degrees C. To prevent misleading results, it is recommended that cerebrospinal fluid specimens not be left at room temperature for prolonged periods of time prior to lactic acid determination.