Ann Lab Med.  2013 Mar;33(2):105-110. 10.3343/alm.2013.33.2.105.

Role of the Neutrophil-Lymphocyte Count Ratio in the Differential Diagnosis between Pulmonary Tuberculosis and Bacterial Community-Acquired Pneumonia

• Yoon NB
• Son C
• Um SJ

• KMID: 1781308
• DOI: http://doi.org/10.3343/alm.2013.33.2.105

Abstract

BACKGROUND
Differential diagnosis between pulmonary tuberculosis (TB) and bacterial community-acquired pneumonia (CAP) is often challenging. The neutrophil-lymphocyte count ratio (NLR), a convenient marker of inflammation, has been demonstrated to be a useful biomarker for predicting bacteremia. We investigated the usefulness of the NLR for discriminating pulmonary TB from bacterial CAP in an intermediate TB-burden country.
METHODS
We retrospectively analyzed the clinical and laboratory characteristics of 206 patients suspected of having pulmonary TB or bacterial CAP from January 2009 to February 2011. The diagnostic ability of the NLR for differential diagnosis was evaluated and compared with that of C-reactive protein.
RESULTS
Serum NLR levels were significantly lower in patients with pulmonary TB than in patients with bacterial CAP (3.67+/-2.12 vs. 14.64+/-9.72, P<0.001). A NLR <7 was an optimal cut-off value to discriminate patients with pulmonary TB from patients with bacterial CAP (sensitivity 91.1%, specificity 81.9%, positive predictive value 85.7%, negative predictive value 88.5%). The area under the curve for the NLR (0.95, 95% confidence interval [CI], 0.91-0.98) was significantly greater than that of C-reactive protein (0.83, 95% CI, 0.76-0.88; P=0.0015).
CONCLUSIONS
The NLR obtained at the initial diagnostic stage is a useful laboratory marker to discriminate patients with pulmonary TB from patients with bacterial CAP in an intermediate TB-burden country.

Keyword

C-reactive protein; Lymphocyte; Neutrophil; Pneumonia; Tuberculosis

MeSH Terms

Adolescent
Adult
Aged
Aged, 80 and over
Area Under Curve
C-Reactive Protein/analysis
Community-Acquired Infections/*diagnosis
Diagnosis, Differential
Female
Humans
Leukocyte Count
Lymphocyte Count
Lymphocytes/*cytology
Male
Middle Aged
Neutrophils/*cytology
Pneumonia, Bacterial/*diagnosis
ROC Curve
Retrospective Studies
Sensitivity and Specificity
Tuberculosis, Pulmonary/*diagnosis
Young Adult
C-Reactive Protein

Figure

• 

  Fig. 1 Patient flow chart.Abbreviations: WBC, white blood cell; CRP, C-reactive protein; FU, follow up; CAP, community-acquired pneumonia; TB, tuberculosis; AFB, acid-fastbacilli.

• 

  Fig. 2 ROC curves of C-reactive protein (CRP) and neutrophil-lymphocyte count ratio (NLR) for discriminating tuberculosis from bacterial community-acquired pneumonia. The area under the curve for NLR (AUC, 0.93; 95% confidence interval [CI], 0.88-0.96) was significantly greater than that for CRP (AUC, 0.83; 95% CI, 0.76-0.88) (P=0.0015).

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