Serum D-lactate: a useful diagnostic marker for acute appendicitis

Acute appendicitis is the most common acute surgical infection seen in emergency department. The present study aims to evaluate the sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) of the serum D-lactate levels as a marker for the diagnosis of acute appendicitis. D-lactate is the stereoisomer of the mammalian L(+)-lactate, and is produced by indigenous bacteria (Escherichia coli, Klebsiella, Bacteroides, Lactobacillus) in the gastrointestinal tract. Once obstruction occurs, appendix is a good medium for bacterial proliferation, and ischemic injury leads to an increase in D-lactate levels.

A total of thirty-two consecutive patients with the suspicion of acute appendicitis were prospectively included in the study. Patient characteristics, ultrasonography (US) and laboratory assessment including white blood cell (WBC), C-reactive protein (CRP), D-lactate and intraoperative findings, histology results, clinical outcome were evaluated.

WBC level above 10(9)/L had an accuracy of 66%, whereas a CRP level above 5 mg/L had an accuracy of 75%. We observed that when the D-lactate level was greater than 0.25 mmol/L in acute appendicitis, the specificity was 60%, the false negative rate was 25% and the accuracy was 90%. The false negative rate of CRP (67%) was higher than that of D-lactate levels (25%). Ultrasound had a sensitivity of 96%, specificity 40% and accuracy 87% in our study.

We found positive correlations between serum D-lactate levels and acute appendicitis and serum D-lactate had the lowest false negative rate among the other parameters. Therefore, we conclude that D-lactate might be a simple and reliable diagnostic marker for appendicitis.