Digital polymerase chain reaction can offer faster diagnosis, higher sensitivity, and broader pathogen detection compared with traditional blood culture, according to a retrospective analysis of 149 patients.
Digital polymerase chain reaction (dPCR) identified 42 positive samples, while culture yielded 6, and dPCR detected bloodstream pathogens in 28% of patients with suspected infection compared with 4% positivity by blood culture. Among the 42 dPCR-positive patients, the researchers noted, there was about a 67% concordance rate (4/6) with blood culture results. When analyzed against culture as the reference standard, dPCR showed a sensitivity of 83% and a specificity of 74%. This relatively low specificity may be due to dPCR's high sensitivity combined with false-negative culture results from antibiotic use, the researchers suggested. In 37 samples that were dPCR-positive but culture negative, nearly half of the patients had received antibiotics prior to sampling, which may have contributed to negative culture results. “In addition, the sensitivity of dPCR is not affected by the application of antibiotics, which makes dPCR more promising in clinical applications,” wrote lead author Min Zhao, PhD, of the Clinical Laboratory at the Affiliated Chenggong Hospital of Xiamen University in China.
The average turnaround time for dPCR was 5 hours, compared with nearly 4 days for culture. Four culture-positive cases matched organisms detected by dPCR. Two pathogens—Salmonella enterica and Streptococcus sanguinis—were not included in the dPCR detection panel and were identified only by culture. Overall, dPCR detected 63 strains across 13 species, including bacteria, fungi, and viruses. The most frequent bacterial findings were Acinetobacter baumannii and Streptococcus species. Cytomegalovirus reached the highest DNA load among viral detections. Pathogen levels varied widely, from 25.5 copies per milliliter (A baumannii) to more than 400,000 copies per milliliter (cytomegalovirus). Polymicrobial infections were reported in 14 patients. Patients with dPCR-positive results had higher inflammatory markers compared with dPCR-negative patients. Median C-reactive protein was 51 mg/L compared with 22 mg/L, and procalcitonin was 0.39 ng/mL compared with 0.19 ng/mL. White blood cell counts were also higher in patients with positive dPCR findings. The age difference between the groups (median age in the positive dPCR group = about 29 years vs 6 years in the negative dPCR group) was statistically significant.
The researchers reviewed medical records from January 2023 to December 2024. Eligible patients had fever on admission, a confirmed infectious focus, and elevated inflammatory markers. Blood samples were tested by both standard culture and droplet-based dPCR using a fixed target panel. The assay’s limit of detection ranged from 0.5 to 1 copy per milliliter depending on the pathogen. Limitations included the single-center and retrospective design, as well as the relatively small number of pathogen-positive cases. The assay panel did not cover all clinically relevant organisms, such as S enterica and S sanguinis. Because dPCR can detect DNA from nonviable organisms, some positive results may not have represented active infection. Serial testing was not performed to assess pathogen loads over time. The authors plan to collect continuous samples to evaluate dPCR's value in assessing antimicrobial therapy efficacy.
The authors reported no conflicts of interest.
Source: Frontiers
