Procalcitonin shows moderate accuracy for bloodstream infection detection in retrospective cohortBlood test shows promise in detecting bacterial infections and identifying their type

Frontiers in Medicine Published April 4, 2026 DOI ↗ Editorial oversight: Dr. Amelia Tan, PhD · Internal Medicine & Chronic Disease

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Key Takeaway

Consider PCT as an adjunct biomarker for BSI detection, but recognize it cannot reliably differentiate Gram-negative from Gram-positive infections.

This retrospective cohort study analyzed 275 positively flagged blood culture bottles (251 isolates analyzed) from a single centre in South India to evaluate the diagnostic utility of procalcitonin (PCT) in bloodstream infections (BSIs). The bacterial distribution was 77.68% Gram-negative and 22.31% Gram-positive pathogens, with Escherichia coli (46.3%) and Klebsiella pneumoniae (44.29%) being the most common Gram-negatives. PCT measurement showed mean levels of 37.87 ng/mL in Gram-negative infections versus 35.09 ng/mL in Gram-positive infections. For BSI detection overall, PCT demonstrated 77.41% sensitivity, 91.04% specificity, and 82.87% diagnostic accuracy.

Safety and tolerability data were not reported in this diagnostic accuracy study. The study has key limitations including its retrospective design and single-centre setting, which may limit generalizability. The overlapping PCT values between Gram-negative and Gram-positive groups and the lack of statistical comparisons for these means further constrain interpretation.

In practice, these observational data suggest PCT may serve as a useful adjunctive biomarker for early BSI detection when interpreted alongside clinical and microbiological findings. However, the marginal difference in mean PCT levels between pathogen groups and the study's design limitations mean PCT cannot reliably differentiate Gram-negative from Gram-positive infections and should not be used as a standalone diagnostic tool.

Researchers wanted to see if a blood test called procalcitonin (PCT) could be useful for spotting serious bacterial infections in the bloodstream and for giving an early clue about the type of bacteria causing it. They looked back at data from 275 positive blood culture samples from a single hospital in South India. Most of the infections (about 78%) were caused by Gram-negative bacteria, with E. coli and Klebsiella pneumoniae being the most common.

The study found that the PCT test was good at detecting a bloodstream infection, with about 82% overall accuracy. The average PCT level was a bit higher in infections caused by Gram-negative bacteria (37.87 ng/mL) compared to Gram-positive bacteria (35.09 ng/mL). However, this difference was small, and the levels overlapped a lot between the two groups.

It's important to be careful with these results. This was a retrospective study, meaning researchers looked at old records, which can limit how strong the findings are. The work was done at just one hospital, so the results might not be the same everywhere. The PCT test should not be used alone to decide what type of bacteria is causing an infection. Doctors will still need to rely on full blood culture results and a patient's overall condition to make the best treatment decisions.

What this means for you:

A blood test may help detect serious infections, but it cannot reliably tell bacteria types apart on its own.

Study Details

Study typeCohort

EvidenceLevel 3

PublishedApr 2026

View Original Abstract ↓

BackgroundBloodstream infections (BSIs) are significant contributors to global morbidity and mortality, with sepsis accounting for 11 million deaths annually. Accurate and rapid diagnosis is essential for effective management.MethodsThis retrospective analysis was conducted on 275 positively flagged blood culture bottles collected over one year. Samples were processed using automated blood culture systems, followed by pathogen identification and antimicrobial susceptibility testing (AST) via the Vitek-2 Compact system (bioMérieux, France). PCT (Procalcitonin) levels were measured using MINIVIDAS (bioMérieux, France) and correlated with pathogens to evaluate diagnostic accuracy.ResultsAmong 251 isolates, Gram-negative bacteria predominated (77.68%), with Enterobacterials like Escherichia coli (46.3%) and Klebsiella pneumoniae (44.29%) being the most common. GP (Gram-positive) bacteria accounted for 22.31%, led by Staphylococcus aureus and Enterococcus species. The mean PCT levels were higher in GN (Gram-negative) infections (37.87 ng/mL) than in GP infections (35.09 ng/mL). PCT demonstrated a sensitivity of 77.41%, specificity of 91.04%, and diagnostic accuracy of 82.87%.ConclusionPCT levels were elevated in both Gram-negative and Gram-positive BSIs, with marginally higher values in Gram-negative infections. Significant elevations in Gram-positive infections, particularly with Streptococcus and Staphylococcus species, highlight their broader diagnostic relevance. With good sensitivity and high specificity, PCT serves as a useful adjunctive biomarker for early BSI detection and may support preliminary differentiation of pathogen groups when interpreted alongside clinical and microbiological findings.

Procalcitonin shows moderate accuracy for bloodstream infection detection in retrospective cohortBlood test shows promise in detecting bacterial infections and identifying their type

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Procalcitonin shows moderate accuracy for bloodstream infection detection in retrospective cohortBlood test shows promise in detecting bacterial infections and identifying their type

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