Cerebrospinal fluid lactate: measurement of an adult reference interval.

BACKGROUND: Differentiating bacterial meningitis from viral meningitis is a diagnostic challenge. Cerebrospinal fluid lactate has been proposed as a valuable test to differentiate disease states; however, its use in adults is limited by a lack of robust reference interval data. METHODS: Cerebrospinal fluid samples with no cells or organisms detected, no culture growth after 48 h, and no increase in cerebrospinal fluid bilirubin were used to derive reference interval data for cerebrospinal fluid lactate in adults (n = 120). RESULTS: A cerebrospinal fluid lactate reference interval of 1.0 (90% CI 0.9-1.1) - 2.2 mmol/L (90% CI 2.0-2.6) was defined. CONCLUSIONS: Cerebrospinal fluid lactate results are rapidly available to the clinician. When interpreted against the adult reference interval derived in this study, results can help to triage patients presenting with symptoms of meningitis.

Delayed appearance of markers of intravascular haemolysis in a case of paroxysmal cold haemoglobinuria.

The aetiology of haemolytic disease is diverse and the diagnosis often relies on laboratory testing. We describe a case of intravascular haemolysis, which illustrates that significant intravascular haemolysis can occur in the absence of any abnormal haematological findings. Despite gross haemoglobinuria at presentation, the haemoglobin and reticulocyte counts were both within reference limits and a normal blood film was observed. Subsequently, acute tubular necrosis occurred secondary to haemolysis, and acute renal failure was evident by day 2. However, the haemoglobin decreased slowly reaching a nadir of 75 g/L on day 6 (reference interval 130-180 g/L). A diagnosis of paroxysmal cold haemoglobinuria secondary to mycoplasma infection was subsequently made. Biochemical analysis was useful in this case to confirm that the gross pigmentation in the samples received could be attributable to intravascular haemolysis.