INTRODUCTION
Vermiform appendix has surgical importance as it has tendency to undergo inflammation and cause acute appendicitis. Acute appendicitis is most common cause of acute abdomen in young adults and appendectomy is most frequently performed urgent abdominal procedure1,2. Epidemiologic studies have showed that approximately 50% (13-77%) of the population will have appendicitis in their life time3, with the peak incidence is in teens 20s, while it’s rare in infancy and risk of acute appendicitis decreases after middle age. Incidence is equal among males and females before puberty and increases to 3:2 at age 25, thereafter greater incidence in males decline.
No cause is yet confirmed but the factors responsible can be decreased dietary fibers and increased consumption of refined carbohydrates because incidence in developing countries is gradually increasing as they are adapting more western lifestyle4.
The diagnosis is basically clinical along with lab findings. Therefore combined scoring systems of both has devised to reduce negative appendectomy rates(15-25%)5. Most widely used scoring system is Alvarado scoring system , however RIPASA scoring system is new development in recent years6.
The Raja Isteri Pengiran Anak Saleha Appendicitis (RIPASA) scoring system was established in 2008 specifically for Asian populations. Chong C F in his retrospective study consisting of 312 patients who had undergone an emergency appendectomy between October 2006 and May 2008 in Department of Surgery, Raja Isteri Pengiran Anak Saleha (RIPAS) Hospital, Brunei Darussalem, concluded that optimal cut-off threshold score for negative appendectomy was 7.5, with a sensitivity of 88%, a specificity of 67%, a PPV of 93% and an NPV of 53%. The negative appendectomy rate decreased significantly from 16.3% to 6.9%, which was a 9.4% reduction (p is 0.0007)6.
Another study conducted at CMH Kohat by Muhammad Qasim Butt from sept 2011 to march 2012 showed that, out of 267 patients, positive cases of acute appendicitis on histopathology were 152 and RIPASA score diagnosed 155 cases of acute appendicitis. True positive were 147, false positive 8, false negative 5, and true negative 107. Sensitivity of RIPASA score was 96.7%, specificity 93.0%, diagnostic accuracy was 95.1%, positive predictive was 94.8% and negative predictive was 95.54%3.
There is scarce local data available on this topic in our region and internationally so, the aim of our study is to evaluate the diagnostic accuracy of this new scoring system for presumptive accurate diagnosis of acute appendicitis by taking histopathology as gold standard. This study might be helpful in order to eliminate negative appendectomy rates in our local population.
Materials and methods
This Cross sectional study was carried out at Surgery department of a tertiary care hospital, Karachi. The study was conducted over a duration of six months from 15th December 2019 to 15th June 2020. Non – probability consecutive sampling technique was used. By using sample size calculator for sensitivity and specificity by Dr. Lin Naig , statistics found as follows3:
Sensitivity = 96.7%
Specificity = 93%
Prevalence of acute appendicitis = 50%
Margin of error for sensitivity = 4.2% and specificity = 6%
The calculated sample size came out as 141. Our inclusion criteria was : (i) Both genders , Male/Female (ii) Age 15 – 50 years (iii) Suspected cases of acute appendicitis presenting with pain right iliac fossa and VAS(visual analog scale) score = 4 or more in emergency department within 48 hours of onset of pain (score 1-3 = no to mild pain, score 3.1-6= mild to moderate pain, score 6.1-10= moderate to severe pain). The exclusion criteria was : (i) Patient with co-morbid ( HTN , IHD , CLD , AKI , CKD , DM ) by taking detailed history (ii) Patients with history of appendectomy confirmed by examination and previous medical record (iii) Pregnant females confirmation by taking history (iv) Diagnosed cases of appendicular abscess which are confirmed by detailed examination and medical record of patients (ultrasound and CT scan). The parameters of RIPASA scoring system are : age (≤ 40 years =1 point; >40 years =0.5 point), gender (male = 1 point; female = 0.5 point), right iliac fossa (RIF) pain = 0.5 point, migration of pain to RIF = 0.5 point, nausea and vomiting =1 point, anorexia =1 point, duration of symptoms (≤48 hours = 1 point; >48 hours = 0.5 point), RIF tenderness =1 point, guarding = 2 points, rebound tenderness =1 point, Rovsing’s sign = 2 points, fever =1 point, raised white cell count = 1 point, negative urinalysis =1 point and foreign national registration identity card =1 point. The cut-off limit of 7.5 points was deemed as positive for acute appendicitis and was used as a diagnostic tool7.
After approval by ethical review committee, patients were selected after taking written informed consent prior to inclusion in study . Those patients presenting in Emergency with pain right iliac fossa were included. Patients underwent detailed history, general and physical examination and scoring of patients according to RIPASA scoring scale and then decision of appendectomy was taken on the basis of RIPASA score. Patients were observed by same researcher to exclude observer/interviewer bias. Patient’s particulars were noted and a performa was filled and attached with admission form. Removed appendix samples were sent for histopathology (Gold Standard), for confirmation of acute appendicitis.
The data was analyzed using SPSS version 23. Mean and standard deviation was calculated for age and RIPASA score. Frequency and percentage was calculated for gender, education, findings on RIPASA and histopathology. 2×2 table was used to calculate sensitivity, specificity, PPV , NPV , diagnostic accuracy for RIPASA scoring system taking histopathology as gold standard.
Effect modifiers like age, education, socio-economic status and gender were addressed through stratification. Post stratification positive predictive value(PPV) , negative predictive value(NPV) , diagnostic accuracy(DA) , sensitivity and specificity was done.