Appendicitis is sufficiently common and appendectomy is the most frequently performed abdominal operation. The incidence of appendicitis is 1.5–1.9/1000, and it is ∼1.4 times greater in men than in women [7].
The definitive diagnosis of acute appendicitis is only possible with histopathology results after appendectomy. However, the decision to perform surgery is based solely on clinical evaluation supported by laboratory data. Therefore, diagnostic errors are common, resulting in perforation. Ultrasonography and CT scan are used nowadays [2]. Nevertheless, ultrasonography cannot replace clinical evaluation due to false-negative rates and non-availability in many medical institutes, which forces many surgeons to depend on clinical evaluation [8].
Various scoring systems have been developed to support the diagnosis of acute appendicitis [2]. The classic Alvarado score is one of them and included left shift of neutrophil maturation yielding a total score of 10. However, in 1994, Kalan et al. omitted this parameter and produced a modified score. The Modified Alvarado Score (MASS) has comparable sensitivity and specificity to the classic Alvarado score, which were observed if the scores were applied to various populations and clinical settings, usually with worse yield when applied outside the population in which they were originally created [9].
RIPASA scoring system for acute appendicitis was developed at 2010. Since the presentation of the system, it has been studied in Eastern and Western populations. There was a large foreign labor workforce in Brunei Darussalam, who must pay for their medical treatment at RIPAS Hospital. For this reason, foreign nationals tend to present much later when the symptoms are more severe. So they added the parameter of foreign NRIC in the score in these countries. Similar results have been demonstrated with the exclusion of the foreign identity card parameter, thus modified RIPASA developed [10].
So, this study aimed at comparing the diagnostic accuracy of modified RIPASA and MASS in diagnosing patients with acute appendicitis at emergency department of Suez Canal University hospital.
The present study was designed as an observational cross-sectional study that included 40 patients presented to emergency department at Suez Canal University hospital with abdominal pain and suspected clinically as acute appendicitis.
Regarding the baseline characteristics of the study population, this study showed that the mean age of the patients was 30.10 ± 9.69 years with range from 19 to 50 years. Patients aged from 18 to 27 years formed 50% of the patients, followed by (28 – 37) age group who formed 25%, then patients aged (38-47) years old formed 20% and patients of (48 – 57) age group formed only (5%) as shown in Table 1.
Reddy et al. at 2020 prospectively evaluated RIPASA score in 100 patients. The highest incidence of acute appendicitis (38%) was observed in age group of 21-30 years [11].
Our study showed male predominance, with 55% of male patients compared with 45% of female patients as shown in fig. 1. This is in agreement with other study in Africa by Malik et al. that showed male predominance [7]. Similarly, Chong et al. study about the development of RIPASA score, also showed the same proportion of male predominance where male to female ratio was 1.4:1 [12].
Contrast finding was reported at a retrospective survey carried out at south India by Naveen et al. at 2013 which revealed higher prevalence of appendicitis in females (51.7%), compared to males (48.2 %) [13].
According to the Clinical and laboratory measures of the studied population of our study, all the patients presented with right iliac fossa tenderness (100%), rebound tenderness (90%), and nausea/ vomiting (70%). Regarding investigations, only 45% of studied patients had elevated White blood count and 55% had negative urine analysis as shown in Table 2.
Similarly, Reddy et al. study showed that all of the studied patients were suffering from acute right iliac fossa pain (100%) [11].
Regarding the histopathological analysis of appendices of the studied patients showed that 40% of the patients had suppurative appendicitis, one quarter of them had catarrhal appendicitis and only 20% had complicated perforated appendicitis. Meanwhile, about 15% had normal (negative) appendices as shown in fig. 2.
Reddy et al. study reported that on histopathology, 90 patients were proven appendicitis (out of 90 cases, 40 reported as acute appendicitis, 23 as peri-appendicitis, 25 as acute suppurative and 2 cases as gangrenous appendicitis) and 10 negative cases were reported as (all of them were reactive lymphoid hyperplasia) [11] .
Study by Park et al. at 2013 reported a negative appendectomy rate of 15% [14]. This may be due to late presentation or misdiagnosis.
Concerning the diagnostic accuracy of both MASS and modified RIPASA scores, in this studied patients had mean modified RIPASA of 9.70 ± 2.12 points with range from 7 to 15 points as shown in Table 5.
. 75% of the patients had high probability of having appendicitis diagnosis and 20% had confirmed diagnosis based on modified RIPASA scoring system as shown in fig. 3. Modified RIPASA showed a good discriminative ability in our study where the area under the curve for modified RIPASA was 0.902 (95% CI: 0.798 – 1.00) (p=0.002). Moreover, a value of 8.5 or higher was found to be the best cut-off point to predict acute appendicitis among patient with clinically suspected acute appendicitis with sensitivity = 70.6%, specificity = 100% positive predictive value of 100 %, and negative predictive value of 37.5 % and 75% accuracy as shown in Table 6 and Fig. 4. While the area under the curve for MASS was 0.324 (95% CI: 0.137 – 0.510) (p=0.173). Moreover, a value of 5.5 or higher was found to be the best cut-off point to predict acute appendicitis among patient with clinically suspected acute appendicitis with sensitivity = 47.1% and specificity = 33.3%, positive predictive value of 80 %, negative predictive value of 10% and accuracy 45% as shown in Table 9 and Fig. 5 .
Our study found a poor agreement between modified RIPASA score and modified Alvarado score in diagnosis of appendicitis in patients (K=0.201) as shown in Table 10.
Reddy et al. study reported that on comparing both scores, Both p values were statistically significant. ROC curve shows a larger area under the curve for modified RIPASA when compared to MASS . This study also found that the cut-off score to diagnose acute appendicitis in modified RIPASA was fixed at 7.5 which yielded 90 % sensitivity and 72% specificity (which was higher for modified RIPASA score than MASS),positive predictive value 89% and NPV was 30% (the positive predictive value was higher for MASS and negative predictive value was higher for modified RIPASA score) [11].
Another study carried out at 2017 by Kumar et al. reported similar values, where sensitivity, specificity, PPV, NPV and accuracy of 84.2%,100%,100%,85% and 25% respectively [15].
Whereas Rathod et al. at 2015 reported 82.6% and 66.7% specificity and sensitivity respectively for modified RIPASA score [10].
Another study by Sammalkorpi et al. at 2014 found that a cut off value for positive MASS to be more than or equal to 7, showed better diagnostic parameters on these cut off values. When applied to patients, the MASS showed poor sensitivity, poor diagnostic accuracy, and good specificity (with a sensitivity of 59.6%, specificity of 87.5%, PPV of 96.9%, NPV of 25.0%, and diagnostic accuracy of 63.3%) [16].
Similar poor results of MASS were found in another study by Reyes-García et al. that applied the score for non-European populations at 2012, which reported area under the curve for MASS is 0.89. If surgical decision had been based on the modified Alvarado score, negative appendectomies would have been encountered in 18.3% of patients [17].
This study found that younger age, male gender, nausea/ vomiting and guarding were significant predictors for acute appendicitis according to modified RIPASA diagnosis in our study.
Reddy et al. reported that parameters like age, sex, duration of symptoms were also significant and have to be considered for diagnosis according to modified RIPASA [11].
Study limitations
The design of the study which is cross sectional which has low precision and affect validity of results as there was difficulty in defining the time of onset of symptoms.