Diagnosis of Acute Appendicitis using Alvarado Score, Ultrasound Abdomen, and C-Reactive Protein in Different Combinations: A Prospective Observational Study

Abstract

Introduction: Appendicitis is the most commonly encountered surgical emergency worldwide. Numerous diagnostic methods, including clinical scoring systems, radiological modalities, and laboratory markers have been suggested over time to diagnose appendicitis correctly, but a Negative Appendectomy Rate (NAR) of 20-30% is still maintained. Aim: To determine the effect of using all three modalities together i.e., a clinical modality {The Alvarado Score}, a radiological modality {Ultrasound (US)}, and a laboratory parameter {C-Reactive Protein (CRP)} in diagnosing acute appendicitis. Materials and Methods: This was a hospital-based, prospective observational study, carried out in the Department of General Surgery, SMS Medical College, Jaipur, Rajasthan, India, from March 2019 to June 2020. The three diagnostic modalities were arbitrarily categorised into different combinations: Combination 1: Alvarado score ≥5 with C-Reactive Protein (CRP) ≥0.8; Combination 2: Alvarado score ≥5 with US grade 4 with CRP ≥0.8; Combination 3: Alvarado score ≥5 with US grade 4 with CRP ≥4); and the individual modalities i.e., the alvarado score and the US abdomen were also categorised into four categories each. Each of the individual modalities along with their different combinations were tested for their sensitivities, specificities, Positive and Negative Predictive Values (PPV, NPV) etc. Chi-square and t-test, sensitivity test and Receiver Operating Characteristic curve (ROC) and, Analysis of Variance (ANOVA) was used. Results: Total 200 cases were analysed in this study with mean age 32.33±15.78 years. Alvarado score had a sensitivity and specificity of 95.83% and 75%, respectively. US had a sensitivity and specificity of 71.35% and 75%, respectively while CRP had the highest sensitivity with 98.96%, but very low specificity (37.5%). The sensitivity, specificity, PPV and NPV of the combination 1 were found to be 98.96, 37.50, 97.44, 60.00, and of combination 2 was found to be 70.83, 87.50, 99.27,11.11 and for combination 3 was 56.77, 100, 100, 8.79, respectively. Combination 2 also had the highest Area Under Curve (AUC) in Receiver Operating Characteristic (ROC) curve. (Combination 1- 0.661; combination 2- 0.742; combination 3- 0.727). Conclusion: The Combination 2 of three modalities proved to be the best diagnostic tool in the present study. It can pave the way, for a better diagnostic scoring system and future studies in this field.

Keywords

• appendicitis scoring systems
• diagnostic modalities
• negative appendectomy rates