P167 Diagnostic accuracy of neutrophil-lymphocyte ratio in suspected paediatric inflammatory bowel disease

Abstract

Background: Faecal calprotectin has an established role in the investigation of paediatric inflammatory bowel disease (PIBD) but may not be available. Availability is often hampered by non-provision of samples or delayed by long turnaround times. Exploration of other indices which may indicate a strong likelihood of PIBD in the absence of faecal biomarkers remains important. The neutrophil-lymphocyte ratio (NLR) can be calculated from a full blood count (FBC) and has been proposed as a marker of inflammation. We aimed to determine the diagnostic accuracy of NLR in suspected PIBD patients prior to their first endoscopic assessment. Methods: Children (aged <18 yrs) undergoing endoscopic assessment for suspected PIBD were identified from our prospective regional IBD database and local endoscopy lists. Review of laboratory records identified the FBC performed closest and prior to endoscopy. Patients were eligible for inclusion if complete FBC data was available within 6 months prior to endoscopy, during the initial diagnostic cycle. Statistical analyses were performed using Vassarstats and EasyROC v1.3. Results: 182 patients met the inclusion criteria; 89 cases of PIBD and 93 cases with non-IBD diagnoses or normal investigations. The PIBD group were older (12.6yr vs 8.8yr; p<0.0001) with no difference in sex ratio (p=0.575). Median time from blood sample to endoscopy was 16 days (IQR 0–49) and was lower in the PIBD group (4d vs 37d; p<0.0001). NLR was significantly higher in PIBD (median 3.04, IQR 2.03–4.18) than in non-IBD patients (1.4, 0.95–2.03) (p<0.0001). Area under the receiver operator curve (AUROC) for NLR as a diagnostic test for PIBD was 0.81 (95% CI 0.75–0.88). Using an optimal cut-off of 2.37 gave a sensitivity of 67% (95% CI 57–77) and specificity 85% (95% CI 76–92). In patients with otherwise normal blood markers (CRP, ESR, albumin, WCC, platelets), median NLR remained significantly higher in PIBD (2.32 [1.74–3.28] vs 1.43 [1.01–1.97]; p<0.001, AUROC 0.77 [95% CI 0.65–0.89]). Using any abnormal test from CRP, ESR, albumin and NLR, sensitivity was 86% (95% CI 77–92), specificity 66% (95% CI 54–76), positive predictive value 74% (95% CI 64–83) and negative predictive value 80% (95% CI 68–89). Conclusions: NLR is significantly higher in patients with PIBD compared to cases with non-IBD diagnoses or normal investigations. This remains the case in patients with normal inflammatory markers. NLR provides moderate sensitivity and specificity for the diagnosis of PIBD and sensitivity is improved by combination with other readily available blood parameters. We propose that NLR has a useful place in the diagnostic work-up of patients with PIBD, especially in the resource-poor setting and where there are barriers to obtaining faecal samples.