From the Guidelines
Elevated WBC counts, particularly those above 14,000 cells/mm3, warrant a careful assessment for bacterial infection in patients with suspected infection, regardless of the presence of fever. When evaluating elevated WBCs, it's crucial to consider the complete blood count with differential to determine which specific cell types are increased, as this helps identify the likely cause 1. The presence of a left shift, characterized by an increased percentage of band neutrophils or metamyelocytes, also indicates a high probability of bacterial infection 1.
Key Considerations
- Normal WBC counts range from 4,500 to 11,000 cells per microliter, with levels above this indicating leukocytosis.
- Bacterial infections often cause significant increases in neutrophils, sometimes creating "left shift" where immature neutrophils enter circulation.
- The degree of elevation can indicate infection severity, with very high counts (above 25,000-30,000) potentially signaling serious bacterial infections like sepsis, pneumonia, or meningitis.
- Other inflammatory conditions like autoimmune disorders, tissue damage, and certain medications can also cause WBC elevation, so clinical context is essential for proper interpretation.
Diagnostic Approach
- A CBC count, including peripheral WBC and differential cell counts, should be performed for all patients suspected of having infection within 12–24 h of onset of symptoms (or sooner, if the patient is seriously ill) 1.
- The presence of an elevated WBC count or a left shift warrants a careful assessment for bacterial infection, with or without fever 1.
- In the absence of fever, leukocytosis, and/or left shift, or specific clinical manifestations of a focal infection, additional diagnostic tests may not be indicated due to the low potential yield 1.
From the Research
Elevated WBC in Infection
- An elevated white blood cell (WBC) count can be an indicator of infection, particularly bacterial infection 2
- Leukocytosis, or an elevated WBC count, can be caused by various factors including malignant and nonmalignant conditions, and it is essential to use age- and pregnancy-specific normal ranges for the WBC count 2
- A repeat complete blood count with peripheral smear may provide helpful information in diagnosing the cause of an elevated WBC count, such as the types and maturity of white blood cells, uniformity of white blood cells, and toxic granulations 2
Diagnostic Value of Clinical and Laboratory Variables
- Clinical and laboratory variables such as C-reactive protein (CRP), procalcitonin (PCT), interleukin 6 (IL-6), lipopolysaccharide binding protein (LBP), white blood cell count (WBC), neutrophils, respiratory rate (RR), and haemoglobin (Hb) level can be used to predict infections that require antibiotic treatment 3
- In a multivariate analysis, WBC, Hb, RR, and CRP remained independent predictors of the need for antibiotic treatment 3
- Increased levels of PCT, IL-6, LBP, CRP, bilirubin, and RR were significantly associated with bacteraemia, and PCT and IL-6 were also associated with severe sepsis 3
Antibiotic Treatment of Infections
- Recent randomized controlled trials have demonstrated noninferiority of short-course therapy for a range of conditions including community-acquired pneumonia, intraabdominal sepsis, gram-negative bacteraemia, and vertebral osteomyelitis 4
- The in vitro susceptibilities of common pathogens to ertapenem, ciprofloxacin, ceftriaxone, piperacillin-tazobactam, and ampicillin-sulbactam have been studied, and ertapenem has been shown to have high activity against ESBL-producing Escherichia coli and Klebsiella pneumoniae 5
- Ciprofloxacin should not be given for ESBL-producing E. coli and K. pneumoniae due to high resistance rates 5
- The combination of ciprofloxacin and beta-lactam antibiotics may be a probable cause of thrombocytosis, as reported in a case study 6