Correlative Study of Leucocytosis with Microbial Growth Culture Positive and Negative in Various Age Groups

Background: Leucocytosis, a white blood cell (WBC) count above the reference range, is a frequent laboratory finding in hospitalised patients and is often used, alongside inflammatory markers such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), as a bedside clue to underlying infection. However, an elevated total leucocyte count (TLC) is neither perfectly sensitive nor perfectly specific for culture-proven infection, and the relationship between the degree of leucocytosis and actual microbial growth remains incompletely defined across age groups. Objectives: This study was undertaken to determine the prevalence of leucocytosis among patients of different age groups attending a tertiary care institute, and to correlate the degree of leucocytosis with the outcome of microbial culture (positive versus negative), alongside ESR, CRP and peripheral smear findings. Methods: Fifty patients presenting with clinical features suggestive of infection or inflammation were enrolled. Haemoglobin, total and differential leucocyte counts were determined on an automated haematology analyser and by manual peripheral smear examination; ESR was measured by the Westergren/Wintrobe technique; CRP was assessed qualitatively/semi-quantitatively; and specimens (blood, urine, sputum, cerebrospinal fluid, pleural fluid, pus, stool and catheter tips) were cultured on standard bacteriological media under aseptic conditions. Results: Leucocytosis (TLC above 11,000 cells/cumm) was present in 48 of 50 patients (96%), and a raised ESR was seen in 47 patients (94%). Thirty-three of fifty specimens (66%) yielded microbial growth, most commonly Escherichia coli, Staphylococcus aureus and Klebsiella pneumoniae, while seventeen (34%) were culture-negative. CRP was elevated in 45 patients (90%). All 33 culture-positive cases showed concurrent leucocytosis with raised CRP; a substantial proportion of culture-negative cases nonetheless also showed leucocytosis and raised CRP, reflecting non-infective inflammatory states, malaria, and rheumatological disease. Conclusion: Leucocytosis was highly prevalent in this hospitalized cohort and correlated well with culture positivity, but its presence in a sizeable minority of culture-negative patients confirms that TLC alone cannot reliably distinguish infective from non-infective inflammation. A combined panel of TLC, ESR, CRP, peripheral smear morphology, and culture offers a more dependable diagnostic approach than any single marker. Keywords: Leucocytosis; total leucocyte count; C-reactive protein; erythrocyte sedimentation rate; microbial culture; neutrophilia; left shift