Absolute neutrophil count as a diagnostic guide for the use of MRI in the workup of suspected appendicitis in children

Diagnostic accuracy of blood tests of inflammation in paediatric appendicitis: a systematic review and meta-analysis

OBJECTIVE

Possible childhood appendicitis is a common emergency presentation. The exact value of blood tests is debated. This study sought to determine the diagnostic accuracy of four blood tests (white cell count (WCC), neutrophil(count or percentage), C reactive protein (CRP) and/or procalcitonin) for childhood appendicitis.

DESIGN

A systematic review and diagnostic meta-analysis. Data sources included MEDLINE, EMBASE, Central, Web of Science searched from inception-March 2022 with reference searching and authors contacted for missing/unclear data. Eligibility criteria was studies reporting the diagnostic accuracy of the four blood tests compared to the reference standard (histology or follow-up). Risk of bias was assessed (QUADAS-2), pooled sensitivity and specificity were generated for each test and commonly presented cut-offs. To provide insight into clinical impact, we present strategies using a hypothetical cohort.

RESULTS

67 studies were included (34 839 children, 13 342 with appendicitis), all in the hospital setting. The most sensitive tests were WCC (≥10 000 cells/µL, 53 studies sensitivity 0.85 (95% CI 0.80 to 0.89)) and absolute neutrophil count (ANC) (≥7500 cells/µL, five studies sensitivity 0.90 (95% CI 0.85 to 0.94)). Combination of WCC or CRP increased sensitivity further(≥10 000 cells/µL or ≥10 mg/L, individual patient data (IPD) of 6 studies, 0.97 (95% CI 0.93 to 0.99)).Applying results to a hypothetical cohort(1000 children with appendicitis symptoms, of whom 400 have appendicitis) 60 and 40 children would be wrongly discharged based solely on WCC and ANC, respectively, 12 with combination of WCC or CRP.The most specific tests were CRP alone (≥50 mg/L, 38 studies, specificity 0.87 (95% CI 0.80 to 0.91)) or combined with WCC (≥10 000 cells/µL and ≥50 mg/L, IPD of six studies, 0.93 (95% CI 0.91 to 0.95)).

CONCLUSIONS

The best performing single blood tests for ruling-out paediatric appendicitis are WCC or ANC; with accuracy improved combining WCC and CRP. These tests could be used at the point of care in combination with clinical prediction rules. We provide insight into the best cut-offs for clinical application.

PROSPERO REGISTRATION NUMBER

CRD42017080036.

Magnetic resonance imaging (MRI) for diagnosis of acute appendicitis

BACKGROUND

Appendicitis remains a difficult disease to diagnose, and imaging adjuncts are commonly employed. Magnetic resonance imaging (MRI) is an imaging test that can be used to diagnose appendicitis. It is not commonly regarded as a first-line imaging test for appendicitis, but the reported diagnostic accuracy in some studies is equivalent to computed tomography (CT) scans. As it does not expose patients to radiation, it is an attractive imaging modality, particularly in women and children.

OBJECTIVES

The primary objective was to determine the diagnostic accuracy of MRI for detecting appendicitis in all patients. Secondary objectives: To investigate the accuracy of MRI in subgroups of pregnant women, children, and adults. To investigate the potential influence of MRI scanning variables such as sequences, slice thickness, or field of view.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and Embase until February 2021. We searched the references of included studies and other systematic reviews to identify further studies. We did not exclude studies that were unpublished, published in another language, or retrospective.

SELECTION CRITERIA

We included studies that compared the outcome of an MRI scan for suspected appendicitis with a reference standard of histology, intraoperative findings, or clinical follow-up. Three study team members independently filtered search results for eligible studies.

DATA COLLECTION AND ANALYSIS

We independently extracted study data and assessed study quality using the Quality Assessment of Studies of Diagnostic Accuracy - Revised (QUADAS-2) tool. We used the bivariate model to calculate pooled estimates of sensitivity and specificity.

MAIN RESULTS

We identified 58 studies with sufficient data for meta-analysis including a total of 7462 participants (1980 with and 5482 without acute appendicitis). Estimates of sensitivity ranged from 0.18 to 1.0; estimates of specificity ranged from 0.4 to 1.0. Summary sensitivity was 0.95 (95% confidence interval (CI) 0.94 to 0.97); summary specificity was 0.96 (95% CI 0.95 to 0.97). Sensitivity and specificity remained high on subgroup analysis for pregnant women (sensitivity 0.96 (95% CI 0.88 to 0.99); specificity 0.97 (95% CI 0.95 to 0.98); 21 studies, 2282 women); children (sensitivity 0.96 (95% CI 0.95 to 0.97); specificity 0.96 (95% CI 0.92 to 0.98); 17 studies, 2794 children); and adults (sensitivity 0.96 (95% CI 0.93 to 0.97); specificity 0.93 (95% CI 0.80 to 0.98); 9 studies, 1088 participants), as well as different scanning techniques. In a hypothetical cohort of 1000 patients, there would be 12 false-positive results and 30 false-negative results. Methodological quality of the included studies was poor, and the risk of bias was high or unclear in 53% to 83% of the QUADAS-2 domains.

AUTHORS' CONCLUSIONS

MRI appears to be highly accurate in confirming and excluding acute appendicitis in adults, children, and pregnant women regardless of protocol. The methodological quality of the included studies was generally low due to incomplete and low standards of follow-up, so summary estimates of sensitivity and specificity may be biased. We could not assess the impact and direction of potential bias given the very low number of high-quality studies. Studies comparing MRI protocols were few, and although we found no influence of MRI protocol variables on the summary estimates of accuracy, our results do not rule out that some MRI protocols are more accurate than others.

Magnetic Resonance Imaging Provides Useful Diagnostic Information Following Equivocal Ultrasound in Children With Suspected Appendicitis

PURPOSE

In Canada, ultrasonography is the primary imaging modality for children with suspected appendicitis, yet equivocal studies are common. Magnetic resonance imaging provides promise as an adjunct imaging strategy. The primary objective of this study was to determine the proportion of children with suspected appendicitis and equivocal ultrasound where magnetic resonance imaging determined a diagnosis.

METHODS

A prospective consecutive cohort of children aged 5-17 years presenting to a tertiary pediatric Emergency Department with suspected appendicitis were enrolled. Participants underwent diagnostic and management strategies according to our local suspected appendicitis pathway, followed by magnetic resonance (Siemens Avanto 1.5 Tesla) imaging. Sub-specialty pediatric radiologists reported all images.

RESULTS

Magnetic resonance imaging was performed in 101 children with suspected appendicitis. The mean age was 11.9 (SD 3.4) years and median Pediatric Appendicitis Score was 6 [IQR 4,8]. Ultrasonography was completed in 98/101 (97.0%). Of 53/98 (54.1%) with equivocal ultrasound, magnetic resonance imaging provided further diagnostic information in 41 (77.4%; 10 positive, 31 negative; 12 remained equivocal). Secondary findings of appendicitis on magnetic resonance imaging in children with equivocal ultrasound included abdominal free fluid (24, 45.3%), peri-appendiceal fluid (12, 22.6%), intraluminal appendiceal fluid (9, 17.0%), fat stranding (8, 15.1%), appendicolith (2, 3.8%), and peri-appendiceal abscess (1, 1.9%). The observed agreement between magnetic resonance imaging results and final diagnosis was 94.9% (kappa = 0.89).

Single institutional experience with initial ultrasound followed by computed tomography or magnetic resonance imaging for acute appendicitis in adults

PURPOSE

The objectives of this study was to assess the performance of ultrasound (US) for suspected appendicitis in adult patients and to evaluated the additive value of short-interval (within 1 week) computed tomography (CT) or Magnetic Resonance Imaging (MRI) after performing an initial US.

METHODS

In this IRB-approved, HIPAA-compliant, retrospective study, electronic medical records (EMRs) were queried for "US appendicitis" performed over a 2-year interval. EMR was reviewed for CT or MRI performed within 1 week of this exam, and if any new or additional information was available at subsequent exam. White count, patient disposition, and pathology, if surgery was performed, were also recorded.

RESULTS

682 patients underwent US for appendicitis over a 2-year duration, age range from 18 to 92 years (average: 30.1 years, M:F = 141:541). Findings showed 126/682 patients with normal appendix, 75/682 uncomplicated appendicitis, and 4/682 with complicated appendicitis. When performed, no additional findings were seen in these groups on short-interval CT or MRI. 2/682 patients had equivocal findings on US but eventually had normal appendix identified on CT. Four hundred and seventy-three patients had non-visualized appendix, of which only 14/473 (3.1%) eventually had appendicitis.

CONCLUSIONS

Ultrasound is an effective initial modality for evaluating appendicitis even in adult patients. Once a normal appendix, uncomplicated or complicated appendicitis is identified on US, no further imaging is necessary. Very few patients with non-visualization of the appendix eventually have appendicitis. Hence, these patients can be managed with active clinical follow-up rather than immediate CT or MRI. Symptoms and clinical scoring systems can be used for triage of these patients.