Alvarado Score Still Holds: A Prospective Comparison of Modified Alvarado Score [MAS] and Appendicitis Inflammatory Response Score [AIRS] as a Diagnostic Aid in Acute Appendicitis

Introduction: In pre-imaging era, diagnosis of appendicitis was based on clinical assessment. To decrease chances of error and negative appendectomy, Alvarado was first to propose a score in 1885. A number of scores were then put forward including modification of Alvarado score. This study aimed to compare two most commonly used systems, MAS and AIRS. Methods: On admission MAS and AIRS were compared in patients of right iliac fossa pain who subsequently underwent appendectomy. Histopathologic examination was taken as gold standard outcome and MAS and AIRS as tests under evaluation. Results: Study analysed 229 patients with a mean age of 32.69 years and male to female ratio of 1.04. Female patients were older than male patients [35.25 and 30.14 years, respectively; p=0.017]. Negative appendectomy rate was just under 4%. Sensitivity, specificity, PPV and NPV of MAS were 85%, 44.4%, 97.4% and 10.8% and for AIRS were 81.8%, 11.1%, 95.7% and 2.4%. Sensitivity in children and adolescents was 90% and 72.5% for MAS and AIRS, respectively. There was no gender difference between the two. AUC for ROC curve of MAS and AIRS was 0.669 [0.474-0.863] and 0.481 [0.285-0.677] with a significant difference [p=0.0003]. Conclusion: Both scores are sensitive, underdiagnose patients as low risk, but don’t leave any patient with advanced appendicitis. MAS outperforms AIRS for all cases of appendicitis as well as advanced appendicitis. Since both scores classify a large number of patients as low risk, before deciding a surgical intervention, an imaging aid should always be welcome.


Introduction
The diagnosis of acute appendicitis, the most common surgical abdominal emergency [ i ] has been a clinical quandary and continues to be so. Though  Patients of all age groups were included provided they underwent appendectomy in the institution. There were no major exclusions except a mismatch in recording of data. Histopathological examination was taken as the gold standard outcome and MAS and AIRS as tests under evaluation.
The recording of data [of MAS and AIRS] was designed in such a way so that each of the scores were recorded by two surgeons independently [ Table 1]. Thus there were 4 surgeons, two of them recorded MAS and two recorded AIRS.
Any mismatch in data recorded by the two surgeons was a criteria kept for exclusion. Data was tabulated and analysed using IBM © SPSS © 20.0 and Microsoft © Excel © 2013.

Results
Over a study duration of 2 years, 267 patients underwent surgery for an indication of appendicular pathology in the institute.
After carefully scrutinizing recorded data, 38 patients who had a mismatch in entries recorded by the two surgeons independently, were excluded.
Thus, data of 229 patients was analysed after the end of the study. Of these 229 patients, 226 patients underwent appendectomy and 3 patients had the intra-operative diagnosis of perforated Meckel's diverticulum and were regarded as negative appendectomies while analysing the data.
Male patients marginally outnumbered female patients by a male to female ratio of 1.04. The mean age of the study population was 32.69 years. Most of the patients were young as half of the patients [50.3%] were in 3 rd and 4 th decade of life.
Children and adolescents formed 23.2% of total cases. The distribution of male and female patients across age groups was a significant observation as the sex ratio reversed from that in favour of males to that of females as the age advanced. Comparing the data with histopathology of the appendix specimen, MAS could truly predict the least possibility of appendicitis in 4 out of 6 patients while in remaining 2 patients the score was borderline. However, in those 94 patients in whom MAS predicted high likelihood of appendicitis, final histology was appendicitis [ Out of 6 patients with final histology of normal appendix, AIRS could predict least possibility of appendicitis in 1 patient, and 5 patients had a preoperative diagnosis of borderline appendicitis. In those 34 patients in whom AIRS predicted definitive appendicitis, no patient was found to have a negative report of appendicitis [ Table 3].
Mean MAS and AIRS of the patients was 6.20 [out of 9] and 6.24 [out of 12], respectively, both in the borderline range. The value of both MAS and AIRS was lower for male patients [6.02 and 6.19, respectively], compared to female patients [6.38 and 6.29 respectively]. However, the difference of mean MAS and mean AIRS between the two genders was not significant [p= 0.076 and 0.699, respectively] concluding both the score predict the probability of appendicitis in a similar way between the two genders.
When the MAS and AIRS were compared independently among the various age groups, we found the scores to be more predictable in middle age group patients compared to those in immediate younger and older age groups. However, predictability again increased in extremes of ages [p<0.001] [ Table 4, Figure 1].
Mean percentage scores of MAS and AIRS were 68.85 and 51.96, respectively [df=228, t=15.13, p<0.001]. For the same patient, MAS could achieve a higher score compared to AIRS and therefore predicted the possibility of appendicitis in a more definite way.     Bold fonts indicate the lower and higher cut-offs for MAS and AIRS, respectively. The final comparison between MAS and AIRS has been done at cut-off 5 [for both] for lower threshold and at cut-off 8 for MAS and 9 for AIRS.    Figure 2].

Discussion
Taking a call for operative intervention in non-traumatic acute abdomen is not easy especially when there is limited access to imaging in an emergency set up. The bulk of these cases are acute appendicitis. Over the study duration of 2 years, 3,285 patients of all age groups were admitted with complaints of either right lower abdomen pain or poorly localized/ diffuse lower abdomen pain in surgery ward. Of these, 267 patients underwent appendectomy constituting 8.13% of the total population of patients presenting with some symptoms suspicious of appendicitis.
Pouget-Baudry reviewed the role of OAS in management of right lower quadrant pain and found a score of less than 4 was associated with absence of appendicitis while more than 6 was significantly associated with acute appendicitis

Conclusion
Both MAS and AIRS are quite sensitive at lower threshold but underdiagnose a fair number of patients as low risk, even when they have appendicitis but don't leave any patient with advanced appendicitis even at a higher threshold. However, MAS outperforms AIRS in most of the parameters for both all cases of appendicitis as well as advanced appendicitis. Both the scores are more predictable in middle age and in extremes of age and can be used in children and old age patients with similar predictability. Since both scores classify a large number of patients as low risk, before deciding a surgical intervention, an imaging aid should always be welcome.
Limitation-We took final histopathology as the gold standard for diagnosis of appendicitis. So those patients who couldn't undergo appendectomy but probably had appendicitis, were excluded from the study thus decreasing the false negatives.