Negative predictive value of sonography in diagnosis of acute appendicitis in Lamphun hospital

Abstract

           Acute appendicitis is one of the most common medical emergency. Nowadays, ultrasound is helpful in diagnosis of ultrasound, particularly in atypical case. In an attempt to determine whether negative predictive value of ultrasound can be use as a reasonable screening tool, we retrospectively reviewed the records of 138 patients (86 males and 52 females, age range 5-90 years) who presented with right lower quadrant abdominal pain and undergoing ultrasound in Lamphun hospital during January 2010- December 2011. The sonographic findings were graded on a 5-point scale, ranging from a normal appendix identified (grade 1) to frankly acute appendicitis (grade 5). The sonographic findings were compared with surgical and pathologic findings. Thirty-six patients (26.1%) had negative sonographic findings, whereas one hundred and two patients (73.9%) had appendicitis on the sonograms. Overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of the method in diagnosing appendicitis were 85.7%, 63.3%, 88.2%, 58.3% and 80.4%, respectively. In conclusion, sonography has a high PPV but low NPV. It is a rapid, simple non-radiation technique that should be the first-pass approach, particularly for the patient with doubtful clinical signs. Further investigation is of value if ultrasound is not diagnostic.