The Clinical Utility of the Neutrophil-to-Lymphocyte Ratio as a Discriminatory Test among Bacterial, Mycobacterium Tuberculosis, and Nontuberculous Mycobacterium Peritoneal Dialysis–Related Peritonitis

Abstract

Key Points Distinguishing Mycobacterium tuberculosis (TB) and nontuberculous Mycobacterium (NTM) from bacterial peritonitis early is often challenging. Delay in diagnosis and treatment of TB/NTM peritonitis often leads to significant morbidity and mortality. The neutrophil-to-lymphocyte ratio is readily calculable, which allows early prompting of TB/NTM peritonitis. Background Distinguishing Mycobacterium tuberculosis (TB) and nontuberculous Mycobacterium (NTM) from bacterial peritoneal dialysis (PD)–related peritonitis (peritonitis) is often very challenging and can lead to a significant delay in diagnosis and treatment. The neutrophil-to-lymphocyte ratio (NLR) is readily calculable and has been shown to be useful in differentiating pulmonary TB from bacterial pneumonia. We are the first group to demonstrate the predictive efficacy of peritoneal dialysate (PDE) NLR in distinguishing TB/NTM peritonitis from bacterial causes in the PD population. Methods We retrospectively reviewed the clinical and laboratory characteristics of all patients with TB/NTM peritonitis, methicillin-sensitive Staphylococcus aureus (MSSA) peritonitis, and culture-negative peritonitis in our tertiary center between July 2000 and July 2020. The diagnostic ability of the blood and PDE NLR for differential diagnosis was evaluated. Results In total, 258 episodes, 38 episodes, and 27 episodes were caused by MSSA, TB, and NTM species, respectively; 364 episodes were culture negative. The PDE NLR level taken at presentation were lowest in the TB peritonitis, followed by the NTM, culture-negative, and MSSA groups, (9.44±13.01, 16.99±23.96, 36.63±32.33, 48.51±36.01; P <0.001, respectively). The area under the receiver operating characteristic curve for the NLR taken at presentation was 0.83 (95% confidence interval, 0.77 to 0.89; P <0.001). A PDE NLR <15 was an optimal cut-off value with sensitivity, specificity, positive predictive value, and negative predictive values of 81%, 70%, 97%, and 22%, respectively. Conclusions The PDE NLR obtained at presentation is a useful and easily accessible marker to discriminate TB/NTM peritonitis from bacterial peritonitis, especially in areas with intermediate TB/NTM burden. The NLR may enable early prompting of TB/NTM peritonitis, allowing specific investigation and treatment to be instigated earlier.

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