A flagged result is not a diagnosis

A point-of-care whole-blood lactate of 3.8 mmol/L is released from the emergency department for an adult with fever and hypotension. The local reference interval is approximately 0.5 to 2.2 mmol/L, and the local critical value is 4 mmol/L. The result is high but not critical in this case. The bench question is what this value adds to a sepsis workup and what it cannot establish.

Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection. Operationally, Sepsis-3 uses suspected infection plus an acute Sequential Organ Failure Assessment (SOFA) score increase of 2 or more points. A biomarker is not that diagnosis. Current guidance states that sepsis should not be ruled in or ruled out with one biomarker or diagnostic test.

Lactate, procalcitonin, and C-reactive protein report different biological signals and run on different clocks. Blood-culture timing adds microbiology context rather than a biomarker result. A result becomes useful when collection conditions, method, clinical findings, and serial direction are visible together. Release the value with its units, method, collection context, and local flag, not a diagnosis.