Syndromic testing for GI infections with QIAstat-Dx

Differentiating stx1 and stx2 in Shiga-like toxin-producing E. coli (STEC) is crucial

Analyzing our QIAsphere Insights epidemiology data from 2023, we saw a greater incidence of stx2-producing STEC detections (1.9% of total) compared to stx1-producing STEC detections (0.7% of total) (1).

This is important because:

• stx2 is strongly associated with severe disease outcomes (2), including hemolytic uremic syndrome (HUS), a serious condition that can lead to kidney failure
• Importantly, antibiotics are contraindicated for patients with STEC infection, as they can increase the risk of HUS (3)
• The fast identification of stx2 can help reduce the risk for serious complications, guide patient management and improve overall patient outcomes

Caution around detecting stx2f-producing STEC, subtype of concern

Leading public health organizations, such as the ECDC and the UK Health Security Agency, have recently highlighted a notable increase in gastrointestinal illnesses linked to stx2f.

This stx subtype is now recognized as a significant emerging threat (4,5).

• Due to its genetic divergence from other stx2 subtypes, standard PCR primers can fail to detect stx2f, leading to potential underreporting (4)
• Unlike some other syndromic tests, QIAstat‑Dx Gastrointestinal Panel 2 effectively detects the stx2f subtype (6,7), ensuring comprehensive diagnostic coverage

Gastrointestinal co-detections are an important contributor to positive tests

Double, triple and even quadruple gastrointestinal co-detections are common, especially in children (8).

Our QIAsphere data corroborates this. We see a variety of co-detection types, including triple detections between a virus, bacteria and parasite (1).

Ct values can help you understand co-detections

When two or more pathogens are co-detected, doctors need to decide which pathogen to act on. This can impact the choice of treatment. Antibiotics that are appropriate for one co-detection (e.g., EPEC and Shigella) might be contraindicated for another (e.g., STEC stx2 and Salmonella).

In cases like these, additional insights from cycle threshold (Ct) values can aid in clinical interpretation.

Clinical case: Seeing beyond the gastrointestinal symptoms with Ct values

Provided by Liliana Gabrielli, MD, Microbiology Unit, IRCCS Azienda Ospedaliero-Universitaria of Bologna, Policlinico di Sant'Orsola, Italy.

• 1.5-year-old child admitted with vomiting, diarrhea and seizures; Suspected hypoglycemia
• QIAstat-Dx Gastrointestinal Panel 2 result came back quickly as positive for: Norovirus (Ct: 17.8); Enteroaggregative E. coli (EAEC; Ct: 29.7); Enteropathogenic E. coli (EPEC; Ct: 32.2); Clostridium difficile toxin A/B (Ct: 30.4)

• Outcome: The low Ct value (17.8) for norovirus supported the clinical diagnosis of norovirus infection. EAEC, EPEC and Clostridium difficile were probably correlated with co-infection/colonization.
• Comprehensive testing is crucial, but additional information may be necessary for clinical interpretation. That's where QIAstat‑Dx stands out, providing easy access to Ct values and amplification curves for enhanced clinical insights.

QIAstat‑Dx Gastrointestinal Panel 2 for immunocompromised lung transplant patients

According to Laurence Armand-Lefevre, PhD, PharmD, Professor of Microbiology at University of Paris Cité and Head of the Bacteriology Department at Bichat-Claude Bernard Hospital, France:

"A few months after the implementation of the QIAstat‑Dx [gastrointestinal panel], physicians in charge of the immunocompromised lung transplant patients asked us to perform multiplex PCR tests for all their patients, whatever their date of hospitalization. Lung transplant patients frequently have diarrhea and the physician needs to know is this diarrhea an adverse effect of the immunosuppressive treatment, which occurs frequently, or due to the acquisition of a GI pathogen. This test was of particular interest for them."

The importance of accurate detection

To provide timely care, you need accurate results. False negatives and false positives can be a major stumbling block. A missed positive can impact on infection control and delay time to appropriate treatment.

False positives can also have serious consequences, masking the true cause of symptoms. A delay in diagnosis, unnecessary implementation of infection control measures and increased hospital costs are all possible.

Norovirus false positives, for example, can have a negative impact on immunocompromised and oncology patients. These patients often experience diarrhea that goes undiagnosed. Accurate pathogen detection – or lack of detection – can improve their clinical management (11).

The QIAstat-Dx Gastrointestinal Panel 2 has a demonstrated specificity of 99.95% for norovirus, ensuring accurate results (9).