Acute appendicitis is one of the most popular emergencies in surgery around the world. The gold standard treatment is appendectomy. However, a debate now exists regarding the possibility of medically treating AA (11). A delay in diagnosis may lead to complications including perforation, abscess formation, peritonitis, and even death (12). However, an increased rate of surgery for normal appendices has undesirable consequences such as post-operative adhesions and ileus (11). These drawbacks to aggressive surgery have led to the use of ultrasonography and CT to reduce the rate of negative appendectomies and improve diagnostic accuracy. However, these additional diagnostic modalities have led to increased financial burdens and health care costs particularly in less developed countries with limited resources (13).
Given these findings and the difficulties of over and underestimation in the diagnosis of AA, several scoring systems have been developed. Since its introduction in 1986, the Alvarado scoring system has been the most popular (14). Subsequently, modified Alvarado scoring systems have emerged to improve the original Alvarado score’s lower specificity and sensitivity when applied in western nations (15). During the past decade, a new scoring system was developed to treat deficiencies in the Alvarado and modified Alvarado scoring systems in Asian populations. The RIPASA scoring system was initiated in 2010, and it depends solely on history, clinical examination, and 2 blood tests (9, 16). The AIR score was initiated parallel to the RIPASA score to overcome the drawbacks of the previous scores. This score incorporates two simple lab tests (WBC count and CRP) in its scheme. The AIR score assesses the intensity of AA in relation to an elevated WBC count together with the percent of segmented neutrophils and CRP(10).
The most common presenting symptom in our study was RIF pain which was present in in almost all cases. A Brazilian study by Von-Muehlenn et al., to compare AIR against the Alvarado score in 147 patients, found RIF pain in 140 patients (95.3%). They reported vomiting in 51.7% and a temperature > 38.5° C in 27.9%, while 90% of our patients had nausea and vomiting and 44% had a temperature > 38.5° C (17). Shuaib et al., in a Middle Eastern study, found the following incidences of clinical symptoms: pain in the right iliac fossa, 99.3%; anorexia, 58.1%; nausea and vomiting, 81%; and fever, 39% (13).
The total negative appendectomy rate in the current study was 8.4%, which is less than the rates documented by Shuaib et al., (13), Chong et al., (17) and Rathod et al., (18) who documented rates of 18.4%, 22.9%, and 20.69%, respectively.
ROC analysis was performed in the present study to ascertain a cut off score for RIPASA with higher sensitivity and specificity by plotting the true positive rate against the false positive rate for different cut points of a RIPASA score. The AUC for the RIPASA system was greater than that of the AIR (Fig. 2). However, when the AIR score was calculated for a score > 8, there was a higher specificity but much lower sensitivity.
To the best of our knowledge, only a few studies have directly compared the RIPASA and AIR scoring systems for the diagnosis of AA. In the present study, the sensitivity of an AIR score > 4 was greater than that of a RIPASA score ≥ 7.5 and significantly better than AIR scores > 8. The sensitivities for an AIR score > 4, an AIR score > 8, and a RIPASA score ≥ 7.5 was 92.25%, 33.09%, and 83.8%, respectively. The specificity of an AIR score > 8 was greater than an AIR score > 4 and a RIPASA score ≥ 7.5, 84.6%, 76.9% and 69.2%, respectively.
The present study illustrates that the negative appendectomy rate (Table 2 and 3) was recorded in AIR score > 4 in 2.2% (6 out of 268) patients subjected to the score and in RIPASA ≥ 7.5 score, it was recorded in 2.9% (8 out of 246 ) of cases, while the AIR score > 8 demonstrates a negative appendectomy rate of 4% of cases. The highest rate of suspected patients who proved later to be truly positive by histopathogy was registered in AIR > 4 score with 97.8% (262 out of 268).
Table 5 illustrates a comparison between the current study and previous studies (16, 19) which evaluated the RIPASA versus the AIR scoring system in the diagnosis of AA. The highest sensitivity and specificity, 93.1% and 91.6%, respectively, were recorded by Karami et al(16). However, Bolívar-Rodríguez et al., in a study performed in Mexico, reported a sensitivity of 97.2% and a specificity of 27.6% (19).These findings show that a RIPASA score with a cut-off > 7.5 can successfully diagnose AA with a greater than 80% accuracy and higher PPV and positive likelihood ratio than 2 of the 3 previously compared studies.
Other studies have compared the RIPASA score to different scoring systems. Shauib et al. (13) reported that a RIPASA score ≥ 7.5 yielded acceptable diagnostic accuracy measures except for a NPV of 78.5%. They found the sensitivity, specificity, PPV, and diagnostic accuracy to be 94.5%, 88.0%, 97.2%, and 93.38%, respectively. Chong et al. (17) reported sensitivity, specificity, PPV, NPV and diagnostic accuracy rates of 98.0%, 81.3%, 85.3%, 97.4%, and 91.8%, respectively, using a score > 7.5. Using the RIPASA score, Rathod et al., (18) determined sensitivity, specificity, PPV, NPV, and diagnostic accuracy of 82.61%, 88.89%, 96.61%, 57.14%, and 83.91%, respectively.
Andersson was the first to implement the AIR scoring system for the diagnosis of AA in 2008. That report noted a sensitivity of 96% and a specificity of 73% with a cutoff threshold > 4 and a sensitivity and specificity of 37% and 99%, respectively when the cutoff point was > 8 (10). In the present study, the AIR score cutoff was examined at two different values, > 4 and > 8. A cutoff point > 4 yielded a sensitivity, specificity, PPV, NPV, and diagnostic accuracy of 92.25%, 76.9%, 96.7%, 47.7%, and 91%, respectively. However, a cutoff point > 8 yielded disappointing results with poor sensitivity, NPV, and accuracy, meaning it would be difficult to exclude truly negative individuals.
A prior study by Karami et al. (16) demonstrated that a RIPASA score cutoff > 8 yielded a sensitivity, specificity, PPV, NPV, and diagnostic accuracy of 78.4%, 91.6%, 98.5%, and 36.6% respectively. Based on our current study, an AIR score > 4 results in the highest diagnosis accuracy for AA of 91% due to its combined abilities to detect truly positive cases in addition to excluding truly negative patients who experience right lower abdominal pain.
In another comparative study similar to ours, Scott et al. found high sensitivities for intermediate and high risk patients with appendicitis (90%), and for patients with advanced appendicitis (98%), when the AIR score was > 5 (20). De Castro et al. noted a 93% sensitivity and 85% specificity for an AIR > 4 (21), while in the current study, the sensitivity and specificity for an AIR > 4 were 92.2% and 76.9%, respectively. This contrasts to a 33% sensitivity and 84.6% specificity with a score set at > 8.
We postulate that both a RIPASA score ≥ 7.5 and an AIR > 4 have a very good ability to detect truly sick patients when they are at high risk. The current era of scoring systems aiding in the preoperative diagnosis of appendicitis could help to avoid unnecessary laparotomies. The current study adds more precision to the validity of both AIR and RIPASA as objective tools that can be applied to our population to support decision-making in the management of a patient with suspected AA. Our observed rate of negative appendectomies, 26 out of 310 patients (8.4%), is certainly within an acceptable range.
The RIPASA and AIR scoring systems did not show a significant difference in the diagnosis of AA in an Egyptian population. They both contain easily obtained parameters from the history, physical examination, and a few simple blood tests. Both scoring systems are beneficial for making a quick decision in resource limited and low-middle income countries without the need for imaging assistance.
Managing patients with suspected AA remains a challenge and the recommended management approach is indeed unknown, even after ultrasound, CT, and diagnostic laparoscopy were introduced.