From the Guidelines
The utility of WBCs in the diagnosis of appendicitis is limited when used alone, but when combined with other clinical findings and laboratory results, such as C-reactive protein, it can be a valuable diagnostic tool. The total WBC count is frequently used in the diagnostic evaluation of acute appendicitis, but it is not a consistent predictor when used alone, with a positive likelihood ratio of 2.47 (95% CI 2.06 to 2.95) and a negative likelihood ratio of 0.25 (95% CI 0.18 to 0.36) for an elevated WBC count (>10,000/mm3) 1. However, when the WBC count is greater than 15,000/mm3, the positive likelihood ratio increases to 3.47 (95% CI 1.6 to 7.8) 1.
Some key points to consider when using WBC counts in the diagnosis of appendicitis include:
- The combination of C-reactive protein and WBC count is more helpful in diagnosing appendicitis than either test alone, with a positive likelihood ratio of 23.32 (95% CI 6.87 to 84.79) for the combination of a WBC count of 10,000/mm3 and a C-reactive protein of 8 mg/L 1.
- A normal WBC count does not exclude the diagnosis of appendicitis, especially in early or atypical presentations.
- Serial WBC measurements can be helpful in unclear cases, as a rising count over time increases the likelihood of appendicitis.
- The WBC count is most useful when interpreted alongside physical examination findings, patient history, and other laboratory and imaging studies.
In clinical practice, the WBC count should be used in conjunction with other diagnostic tools and clinical findings to support the diagnosis of appendicitis, rather than relying solely on the WBC count alone 1.
From the Research
Utility of WBCs in Diagnosis of Appendicitis
- The white blood cell (WBC) count is considered a useful test in the diagnosis of appendicitis, but its utility is limited in predicting the severity of the disease 2.
- A study found that a normal WBC count was seen in 11% of patients with pathologically confirmed appendicitis, and there was no difference in age, temperature, gender, or severity of disease in patients with a normal WBC count compared to those with an elevated WBC count 2.
- Another study found that WBC, neutrophil, and neutrophil-to-lymphocyte ratio (NLR) are helpful and useful parameters for diagnosing acute appendicitis and measuring severity, but the use of mean platelet volume (MPV) is not recommended due to its low diagnostic rate and contradictory results 3.
Diagnostic Markers in Acute Appendicitis
- Elevated WCC, C-reactive protein (CRP), and bilirubin can be used as diagnostic markers of acute appendicitis, with significant differences in results between patients with negative and positive appendicitis 4.
- The diagnosis of appendicitis remains multifactorial, and blood tests may help guide the surgeon in decision-making 4.
- The Alvarado score, Pediatric Appendicitis Score, and Appendicitis Inflammatory Response score incorporate common clinical and laboratory findings to stratify patients as low, moderate, or high risk and can help in making a timely diagnosis 5.
Limitations of WBCs in Diagnosis
- WBC count is a poor predictor of severity of disease in the diagnosis of appendicitis, and a normal WBC count does not rule out appendicitis 2.
- The proportion of gangrenous and perforated appendicitis in patients with a normal WBC count is the same as in patients with an elevated WBC count 2.
- Other diagnostic markers, such as CRP and bilirubin, may be more useful in diagnosing acute appendicitis than WBC count alone 4.