Evaluation of the Performance Characteristics of a New POC Multiplex PCR Assay for the Diagnosis of Viral and Bacterial Neuromeningeal Infections

Performance Evaluation of Multiplex Molecular Syndromic Panel vs. Singleplex PCR for Diagnosis of Acute Central Nervous System Infections

Acute central nervous system (CNS) infections, such as meningitis and encephalitis, represent medical emergencies that require rapid identification of the causative pathogen to guide appropriate therapeutic interventions. The QIAstat-Dx® Meningitis/Encephalitis (QIA/ME) is a molecular syndromic panel that enables the simultaneous detection of multiple pathogens and provides the visualization of cycle threshold (Ct) values, offering rapid results for prompt clinical management. This study retrospectively tested, with the QIA/ME panel, 170 cerebrospinal fluid (CSF) samples from patients with CNS infections, confirmed through routine diagnostic workflows. The results were compared with those obtained from bacterial culture and singleplex PCR for viral detection. The QIA/ME demonstrated 100% concordance with reference methods for bacterial and yeast infections. For viral infections, the overall detection rate was 85.9%. Specifically, when singleplex PCR results exceeded 250 copies/mL for DNA viruses and 500 copies/mL for the RNA virus, the concordance rate with the QIA/ME was 96.8%. In contrast, when PCR values were below these thresholds, the concordance rate dropped to 43.8%. A strong overall correlation was observed between the viral load measured by singleplex PCR and Ct values from the QIA/ME (ρ = -0.83, p < 0.001). Only for enterovirus a weak correlation was found (ρ = -0.40, p = 0.056). The QIA/ME panel is an effective diagnostic tool for viral CNS infections, allowing for the visualization of Ct values that reflect pathogen load in samples and which could be useful in guiding clinical decision-making and patient management.

Cerebrospinal fluid multiplex PCR cycle thresholds may predict ICU admission in community-acquired meningoencephalitis

OBJECTIVE

We investigated the relationship between cerebrospinal fluid (CSF) PCR cycle threshold (Ct) values, clinical characteristics, and outcomes in suspected CAM, while assessing QIAstat-Dx® ME Panel concordance with routine diagnostic methods.

METHODS

Frozen CSF from 30 individuals with suspected CAM were analyzed using the QIAstat-Dx® ME Panel. Ct values were categorized as low (≤ 30) or high (>30). Concordance with CSF FilmArray®/culture results was assessed using the Kappa coefficient.

RESULTS

Low Ct values were associated to CSF markers of meningitis and predicted ICU admissions (log-rank P = 0.025), particularly within the first two weeks of hospitalization (85 % for low Ct values versus 50 % for high Ct values, P = 0.041). Ct values were not associated with mortality in the survival analysis (log-rank P = 0.109). Substantial agreement was observed between QIAstat-Dx® and comparators (96.7 %, Kappa 0.839).

CONCLUSIONS

CSF Ct values can assist in risk stratification for timely ICU admission in individuals with CAM.

Validation and evaluation of the performance of QIAstat-Dx gastrointestinal panel in pooled stool samples

In the current study, the analytical sensitivity, analytical specificity, reproducibility, anti-interferences ability, and clinical performance of the QIAstat-Dx Gastrointestinal Panel (GIP) system were evaluated using pooled stool samples. Results showed that the pooled sample test detected the selected ten targets exclusively, with no cross reaction with any other targets of common enteropathogens. The analytical sensitivity of the pooled sample test on QIAstat-Dx GIP system was 102 CFU/ml for Shigella spp., 103 CFU/ml for Salmonella spp., Y. enterocolitica, Enterotoxigenic Escherichia coli, Enteropathogenic E. coli, 104 CFU/ml for V. cholerae, 102 copies/ml for Norovirus, 103 copies/ml for Rotavirus, Astrovirus, Sapovirus, respectively. The Coefficients of variation (CV) during the detection of V. cholerae, Salmonella spp., Y. enterocolitica, Enterotoxigenic E. coli, Enteropathogenic E. coli, Shigella spp., Rotavirus, Norovirus, Astrovirus, and Sapovirus detection was 2.3 %, 2.7 %, 3.9 %, 4.2 %, 1.7 %, 2.6 %, 6.7 %, 1.4 %, 1.3 % and 2.7 %, respectively, indicating the high reproducibility of the pooled sample test, except for Rotavirus. When potentially interfering agents were added, the shifted Ct value was less than the cut off value, suggesting the good anti-interferences ability. During clinical evaluation, the pooled sample test was 97.8 % concordant with gold standard methods (bacterial culture for bacteria and qPCR for viruses). Our results suggest that QIAstat-Dx GIP system could be used for pooled sample test for enteropathogens screening, which would be more economical and could improve throughput while provide comparable test performance.

Performance Evaluation of NovaplexTM Multiplex Real-Time PCR Assay for Detection of Streptococcus agalactiae Serotypes

Streptococcus agalactiae, or group B streptococcus (GBS), is a Gram-positive pathogen with an extended track record of colonization in the gastrointestinal and genitourinary tracts. GBS can induce disease in individuals across all age demographics, yet it predominantly triggers infections in neonates and the elderly. Identification of the serotype is vital for effective management of the disease as it provides critical information for clinicians on the cause of the disease. In this study, we evaluated the rapid, simple, and easy-to-adopt multiplex real-time PCR technique, NovaplexTM (NovaPCR). A total of 131 clinical isolates of different serotypes were tested using NovaPCR. Observations revealed that 129 isolates showed the same observations as LA and conventional mPCR. NovaPCR accurately identified serotypes IV and V, which were first classified as serotype Ia in the LA test and mPCR, and the difference between the traditional (LA test and mPCR) and NovaPCR methods is only 1.52%. Accurate serotype identification is helpful for monitoring the epidemics and achieving optimal clinical outcomes, and NovaPCR showed a reliable, fast, easy-to-interpret, and cost-efficient performance in GBS serotyping.

Comment on Cuesta et al. An Assessment of a New Rapid Multiplex PCR Assay for the Diagnosis of Meningoencephalitis. Diagnostics 2024, 14, 802

In April 2024, the manuscript by Cuesta et al [...].

A multicenter evaluation of the QIAstat-Dx meningitis-encephalitis syndromic test kit as compared to the conventional diagnostic microbiology workflow

PURPOSE

Rapid diagnosis and treatment of infectious meningitis and encephalitis (ME) is critical to minimize morbidity and mortality. Recently, Qiagen introduced the CE-IVD QIAstat-Dx ME panel (QS-ME) for syndromic diagnostic testing of meningitis and encephalitis. Some data on the performance of the QS-ME in comparison to the BioFire FilmArray ME panel are available. In this study, the performance of the QS-ME is compared to the current diagnostic workflow in two academic medical centers in the Netherlands.

METHODS

A total of 110 cerebrospinal fluid samples were retrospectively tested with the QS-ME. The results obtained were compared to the results of laboratory-developed real-time PCR assays (LDTs), IS-pro, bacterial culture, and cryptococcal antigen (CrAg) testing. In addition, the accuracy of the QS-ME was also investigated using an external quality assessment (EQA) panel consisting of ten samples.

RESULTS

Four of the 110 samples tested failed to produce a valid QS-ME result. In the remaining 106 samples, the QS-ME detected 53/53 viral targets, 38/40 bacterial targets, and 7/13 Cryptococcus neoformans targets. The discrepant bacterial results consisted of two samples that were previously tested positive for Listeria monocytogenes (CT 35.8) and Streptococcus pneumoniae (CT 40), respectively. The QS-ME detected one additional result, consisting of a varicella-zoster virus signal (CT 35.9), in a sample in which both techniques detected Streptococcus pyogenes. Finally, 100% concordance was achieved in testing a blinded bacterial ME EQA panel.

CONCLUSION

The QS-ME is a relevant addition to the syndromic testing landscape to assist in diagnosing infectious ME.