Diagnosis of Acute Appendicitis using Modified Alvarado Score and Abdominal Ultrasound

Abstract

Introduction: Acute Appendicitis (AA) requires prompt surgery to prevent complications, and the diagnosis is mostly based on clinical features where scoring systems like Modified Alvarado Score (MAS) have been found to be helpful. However, as clinical findings tend to be subjective, Abdominal Ultrasound (AUS) can be used to add some objectivity to the diagnosis of AA. Aim: The aim of the present study was to assess the effectiveness of MAS and AUS in diagnosing AA. Materials and Methods: The present study was designed as a study of Diagnostic Accuracy and was carried out using STARD guidelines at a Tertiary Care Teaching Hospital in India. Prospective collection of data of 100 consecutive patients (70 male and 30 female) who were taken up for Emergency appendectomy for AA during the period from April 2009 to April 2011 was done. Patients with complicated Appendicitis, e.g., perforation-peritonitis, abscess; appendicular lump and pregnant women were excluded. Sensitivity, specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPV), Likelihood Ratios (LR+ and LR-), Diagnostic Odds Ratio (DOR) and Negative Appendectomy Rate (NAR) were calculated for MAS and AUS by standard statistical calculators. Results: The present study included 70 males and 30 females belonging to various ages ranging from 11-62 years. Majority of patients (42%) were in their third decade of life. A total of 76% of patients who underwent surgery for AA had MAS of ≥7. All the 24% remaining patients had MAS of 4-6. Overall AUS revealed inflamed appendix in 67% cases, while in the rest, either the appendix could not be visualised or was reported as normal. Sensitivity, specificity, PPV, NPV, LR+, LR-, DOR and NAR of MAS and AUS were 81.61%, 61.54%, 93.42%, 33.33%, 2.12, 0.30, 7.10, 6.58%; and 71.26%, 61.54%, 92.54%, 24.24%, 1.85, 0.47, 3.97, 7.46% respectively. Between the sexes, diagnostic parameters of MAS were slightly better in males. In contrast, in females the parameters of AUS fared marginally better. AUS had much better diagnostic accuracy in diagnosing AA in MAS <7, when compared to MAS ≥7. Conclusion: The MAS is a good diagnostic tool for AA and should be adequate in uncomplicated AA, if score is ≥7. In those patients where the score is 4-6, AUS should be added to aid in early diagnosis and prompt surgical management of AA. The AUS is also recommended in female patients with suspected AA.

Keywords

• diagnostic accuracy
• emergency appendectomy
• gender
• negative appendectomy rate