Procalcitonin in Differentiating Enteric Fever from Salmonellosis

Diagnostic Markers

PCT levels rise within 2-3 hours of bacterial infection onset, with higher levels correlating with infection severity (0.6-2.0 ng/mL for SIRS, 2-10 ng/mL for severe sepsis, >10 ng/mL for septic shock) 1
PCT should be used as part of a systematic evaluation that includes clinical examination and directed diagnostic techniques, not as a standalone test 2, 3

Blood cultures remain the gold standard for diagnosis of enteric fever, with a sensitivity of approximately 50% compared to bone marrow culture (which has higher sensitivity) 4
Culture-independent diagnostic testing, including panel-based multiplex molecular diagnostics from stool and blood specimens, should be performed when there is clinical suspicion of enteric fever or diarrhea with bacteremia 4
Additional cultures of bone marrow, stool, duodenal fluid, and urine may be beneficial to detect enteric fever, particularly if antimicrobial agents have been administered prior to testing 4
Serologic tests should not be used to diagnose enteric fever due to poor performance characteristics 4

People with clinical features of sepsis who are suspected of having enteric fever should be treated empirically with broad-spectrum antimicrobial therapy after blood, stool, and urine culture collection 5
For non-typhoidal Salmonella infections, particularly those caused by STEC (Shiga toxin-producing E. coli), antimicrobial therapy should be avoided, especially for STEC O157 and other STEC that produce Shiga toxin 2 5
Empiric therapy should attempt to provide antimicrobial activity against the most likely pathogens based upon each patient's presenting illness and local patterns of infection 6

Daily reassessment of antimicrobial regimen is recommended for potential de-escalation to prevent the development of resistance, reduce toxicity, and reduce costs 6
PCT can be used to support shortening the duration of antimicrobial therapy in sepsis patients and to support the discontinuation of empiric antibiotics in patients who initially appeared to have sepsis but subsequently have limited clinical evidence of infection 7
Serial PCT measurements may be more valuable than a single reading, particularly in post-surgical patients 1

PCT levels alone cannot differentiate sepsis from other causes of SIRS; they should be part of a systematic evaluation that includes clinical examination and directed diagnostic techniques 2, 3
Do not delay empiric antibiotic therapy in critically ill patients while awaiting PCT results if bacterial infection is clinically suspected 1
Remember that PCT can be elevated in non-infectious conditions including shock states and drug reactions 1