Optimising QIAstat-Dx Gastrointestinal Panel Use: Development of a Clinical Score to Predict Paediatric Bacterial Infections

Background: The QIAstat-Dx Gastrointestinal Panel (QGP), a rapid multiplex polymerase chain reaction (PCR) test, provides high diagnostic accuracy for ruling in common gastrointestinal pathogens. Its short turnaround time supports earlier therapeutic decisions and antibiotic stewardship, but its high cost highlights the need for more selective testing. This study aimed to develop a clinical score to identify paediatric patients most likely to have a positive bacterial QGP result. To our knowledge, no such score exists. Methods: We conducted a retrospective study including 70 paediatric patients (median age 1.08 years) who underwent QGP testing between April and October 2025 in a tertiary hospital in Bucharest, Romania. Clinical and biological variables, along with sonographic indicators of bowel inflammation, were evaluated for their association with positive bacterial QGP results. Results: No pathogens were detected in 40% of cases, a single pathogen was detected in 32.9% of samples, two pathogens in 21.4%, and three or more in 5.7%. Bacterial organisms were identified in 45.7% of tests, with Salmonella being most common (17.6% of all tests; 28.6% of positive tests). Of all evaluated variables, fever, bloody stools, C-reactive protein (CRP) > 2 mg/dL, sonographic evidence of bowel inflammation, and exclusion of other infectious foci were included in our prediction score, each assigned one point (with a maximum of 5 points). Other laboratory markers showed no significant association with a positive bacterial QGP result. Receiver operating characteristic (ROC) analysis yielded an area under the curve (AUC) of 0.758 (95% CI: 0.596–0.920, p = 0.005). The optimal cut-off, determined using Youden’s index, was 2.5, with 80% sensitivity and 67.7% specificity. A score ≥ 3 indicated a markedly increased likelihood of a positive bacterial QGP result. Conclusions: The proposed QGP clinical score may support selective use of QGP testing, improving diagnostic efficiency and reducing unnecessary costs. Prospective multicentre validation is warranted.