Why to Use
The PAS has been validated in multicenter studies and may be as good as clinician gestalt at identifying patients who are at low risk for appendicitis versus patients with appendicitis.
When to Use
Use the PAS for children and adolescents who present with acute abdominal pain in whom appendicitis is suspected, especially if the pain is localized to the right lower quadrant.
Low Risk PAS (< 4 points)
Equivocal PAS (4-6 points)
High Risk PAS (≥ 7 points)
Jamie Lovell, MD
Patients who are identified as not low risk (eg, equivocal or high risk) for appendicitis by the PAS should receive nothing by mouth, and the next steps should include administration of intravenous fluids and analgesia, ordering imaging, and/or surgical consultation.
Patients in the low risk group according to the PAS do not have no risk for appendicitis. Emergency clinicians should use clinical discretion to determine if imaging or surgical consultation would help with diagnosis for these patients.
The PAS was developed in 2002 by Dr. Madan Samuel in a prospective cohort study of 1170 patients
aged 4 to 15 years who presented with abdominal pain. Clinical history, physical examination, and laboratory data for these patients were analyzed to identify 8 variables that showed statistical significance for acute appendicitis. A 10-point scoring system was created using these variables.
The PAS has been validated in multiple prospective studies. Bhatt et al (2009) studied 246 children aged 4 to 18 years and found a sensitivity of 97.6%, with a negative predictive value of 97.7%, at a cutoff PAS of ≤ 4 points. When a PAS of ≥ 8 points was used to determine that appendectomy was needed, the specificity was 95.1% and the positive predictive value was 85.2%. In this cohort, 41% of computed tomography scans would have been avoided using the PAS. Goldman et al (2008) evaluated the PAS in 849 children aged 1 to 17 years; the area under the receiver operating characteristic curve was 0.95, although the study used more con-servative cutoffs of ≤ 2 points and ≥ 7 points.
Schneider et al (2007) evaluated both the PAS and the Alvarado score and found that they had similar sensitivity and specificity, but concluded that neither score was sufficient to be relied on as the only method to determine whether appendectomy is needed. Shah et al (2016) developed a diagnostic algorithm and used it prospectively in 840 patients, 267 of whom were ultimately diagnosed with appendicitis. The algorithm was found to have a sensitivity of 98.6% and specificity of 94.4%, with a decrease in utilization of computed tomography from 75.4% to 24.2%.
Madan Samuel, MD
Why to Use
Acute appendicitis is a common surgical emergency in the United States. Diagnostic accuracy for appendicitis is increased with the use of CT scanning; however, there are risks and disadvantages associated with CT scans, including radiation exposure, contrast-related complications, and cost. The Alvarado score is a well-established and widely used clinical decision tool that may help reduce the need for CT scans when diagnosing appendicitis.
When to Use
The Alvarado score can be used for patients with suspected acute appendicitis (typically, patients presenting with right lower quadrant pain).
Ayomide Loye, MD
Xiao Chi Zhang, MD, MS
Clinicians should use clinical judgment in nonclassic presentations of appendicitis.
The Alvarado score was initially described in 1986 by Dr. Alfredo Alvarado in a retrospective study at a single center in Philadelphia. For 305 patients aged 4 to 80 years, 8 predictive factors were identified to stratify the risk of acute appendicitis. Increasing scores were found to correlate with increasing risk for appendicitis, as determined by final surgical pathology.
In 2007, McKay et al studied a retrospective cohort of 150 patients (aged ≥ 7 years) presenting with abdominal pain, with the aim of stratifying risk specifically for the use of computed tomography (CT) scanning for diagnosis. They found 35.6% sen-sitivity for appendicitis based on equivocal Alvarado scores (defined as scores of 4-6) compared with 90.4% sensitivity based on CT scan in this group. They concluded that patients with equivocal scores would benefit from CT scanning.
Similarly, Coleman et al (2018) conducted a retrospective review in which the Alvarado score was applied to a cohort of 492 patients (median age, 33 years), and found that 20% of the patients scores ≥ 9 in men or a score of 10 in women) or the low-risk group (scores ≤ 1 in men and ≤ 2 in women). These patients spent a cumulative total of > 170 hours awaiting CT scanning that was ultimately unnecessary. The authors found that scores of 0 or 1 had 0% incidence of acute appendicitis and that 100% of men with a score ≥ 9 and 100% of women with a score of 10 had acute appendicitis confirmed on surgical pathology.
Pogorelić et al (2015) prospectively studied 311 pediatric patients and applied both the Alvarado score and the pediatric appendicitis score (Samuel 2002). Receiver operating characteristic analysis showed similar accuracy between the scores, with area under the receiver operating characteristics of 0.74 (95% confidence interval, 0.66-0.82) for the Alvarado score and 0.73 (95% confidence interval, 0.65-0.81) for the pediatric appendicitis score. The authors concluded that the scores may be useful in emergency settings, but neither score is superior to the clinical gestalt of a pediatric surgeon.
Alfredo Alvarado, MD
Why to Use
The pARC may help determine the need for advanced imaging such as formal ultrasound or CT scan. It can identify low-risk patients who can be observed in the ED or discharged from the ED with follow-up or return precautions. In a validation study, the pARC formula performed better than the PAS by placing fewer patients into equivocal risk categories, making the pARC potentially more useful than the PAS for aiding clinical decision-making.
When to Use
Use the pARC in children aged ≥ 5 years who present to the ED or outpatient setting with acute abdominal pain with a duration < 96 hours. Patients with the following conditions were excluded from the pARC study:
Patients determined by the pARC to be at low risk for appendicitis can be considered candidates for safe discharge or observation in the ED without advanced imaging such as ultrasound or CT scan, based on the discretion of the emergency clinician and the comfort level of the patient’s family. Given the specificity of the pARC, patients who are classified as high or high-intermediate risk for appendicitis may not need advanced imaging. In the high-risk group, 1.2% of appendectomy specimens were negative for appendicitis on pathology analysis and in the high-intermediate risk group, 2.6% of the specimens were negative.
Derek Tam, MD, MPH
Hector Vazquez, MD
Critically ill patients or patients with emergent “surgical abdomens” (rigidity, visible ecchymosis or hematoma, etc) should not be considered for delayed surgical consultation or imaging. These patients will likely benefit from early consultation with pediatric surgeons and from imaging, if they are able to be transported to radiology.
The pARC formula was derived from a dataset of 2423 patients with an interquartile age range of 8 to 14 years. Candidate predictors with > 10% missing data were not included. Patients with certain comorbid conditions were also excluded (Kharbanda 2018).
While absolute neutrophil count (ANC) was used in the pARC formula, ANC values were missing for 216 (9%) of the patients in the derivation data set. For patients missing the ANC value, it was imputed as ANC = (-0.8783 + 1.1008 x sqrt(WBC))^2. For patients missing both ANC and white blood cell count values, the ANC value was imputed as 7 x 103/mcL, which was the mean ANC value in the derivation cohort. The proportion of missing values was less than the 10% cutoff point chosen by the study authors; however, imputation of missing values has the potential to introduce bias into the equation.
An independent validation study was conducted at different centers and demonstrated the ability of the pARC to outperform the pediatric appendicitis score (Cotton 2019). This study demonstrated a superior area under the receiver operating characteristic curve with nonoverlapping 95% confidence intervals as compared to the pediatric appendicitis score.
Manuel Mutschler, MD
Kharbanda AB, Vazquez-Benitez G, Ballard DW, et al. Development and validation of a novel pediatric appendicitis risk calculator (pARC). Pediatrics. 2018;141(4): e20172699.
Cotton DM, Vinson DR, Vazquez-Benitez G, et al. Validation of the pediatric appendicitis risk calculator (pARC) in a community emergency department setting. Ann Emerg Med. 2019. In press.