From the Guidelines
Chronic osteomyelitis typically does not show elevations in white blood cell counts. Unlike acute osteomyelitis, which often presents with elevated white blood cell counts, chronic osteomyelitis is characterized by persistent infection that has been present for months or years, during which the body's inflammatory response becomes more localized and less systemic. Laboratory markers such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) may be mildly elevated in chronic osteomyelitis, but the white blood cell count usually remains within normal limits, as noted in a study from 1. This is because chronic osteomyelitis involves the formation of a sequestrum (dead bone) surrounded by new bone (involucrum), creating a protected environment where bacteria can persist with minimal triggering of systemic inflammatory responses. The absence of leukocytosis can make laboratory diagnosis challenging, which is why imaging studies like MRI, CT scans, or bone scans are often more valuable for diagnosis than blood tests in chronic cases, as suggested by guidelines from 1 and 1. Some key points to consider in the diagnosis of chronic osteomyelitis include:
- The use of probe-to-bone test, which can be helpful in diagnosing osteomyelitis, especially in high-risk patients 1
- The importance of imaging studies, such as MRI or CT scans, in diagnosing chronic osteomyelitis 1
- The need to consider other diagnostic tests, such as histological and microbiological examinations of aseptically obtained bone samples, when the diagnosis is in doubt or when determining the causative pathogen's antibiotic susceptibility is crucial 1 Clinicians should therefore not rely on white blood cell counts to rule out chronic osteomyelitis when clinical suspicion exists, and instead, use a combination of diagnostic tests and clinical judgment to make an accurate diagnosis.
From the Research
Chronic Osteomyelitis and White Blood Cell Counts
- Chronic osteomyelitis is an inflammatory process of the bone caused by an infectious agent, leading to altered bone vascularization and bone destruction 2.
- The diagnosis of osteomyelitis is usually clinically diagnosed with support from imaging and laboratory findings, including serum inflammatory markers such as white blood cells (WBC) 3, 4.
- Studies have shown that serum inflammatory markers, including WBC, are elevated in patients with osteomyelitis, particularly in those with chronic osteomyelitis 4.
- Specifically, one study found that WBC values were significantly higher in patients with osteomyelitis than in those with soft-tissue infections, with a sensitivity and specificity for the diagnosis of osteomyelitis of 0.75 and 0.79, respectively 4.
- However, it is worth noting that WBC values can return to near-normal levels after initiation of treatment with antibiotics, whereas other inflammatory markers such as erythrocyte sedimentation rate (ESR) may remain high until later stages of treatment 4.
Laboratory Findings in Chronic Osteomyelitis
- Laboratory findings, including WBC counts, can be used to support a clinical diagnosis of osteomyelitis 5, 3.
- Elevated WBC counts can indicate the presence of an infectious process, such as osteomyelitis 4.
- However, it is essential to consider other laboratory findings, such as ESR and C-reactive protein (CRP), in conjunction with WBC counts to confirm a diagnosis of osteomyelitis 4.
Treatment and Management of Chronic Osteomyelitis
- The treatment of chronic osteomyelitis is primarily based on surgical management, including debridement of the sequestrum and sampling of bone tissue for microbiological analysis 2.
- A multidisciplinary approach is essential, involving expertise in orthopedic surgery, musculoskeletal imaging and nuclear medicine, infectious diseases, as well as plastic or vascular surgery for complex cases 2, 6.
- Antibiotics are a crucial component of treatment, and should be tailored based on culture results and individual patient factors 5, 3.