Cath Lab Digest

   It is important to consider both clinical and laboratory tests when assessing and diagnosing osteomyelitis. Laboratory tests, including complete blood count with differential, basic metabolic panel, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), can often be ambiguous or within normal limits despite the presence of infection. The clinical presentation of osteomyelitis can be subtle. Less than 50 percent of patients with diabetes admitted to the hospital with acute osteomyelitis exhibited leukocytosis or systemic symptoms.¹⁰

   Emerging research advocates the use of clinical findings in conjunction with laboratory test as an effective predictor of osteomyelitis. Fleischer and co-workers demonstrated that elevated levels of CRP in combination with an ulceration depth of greater than 3 mm were the most accurate variables when diagnosing osteomyelitis without advanced modalities.¹¹

   The gold standard of diagnosing osteomyelitis continues to be the histological analysis of bone specimens.6 This has allowed physicians to determine the route and duration of antibiotics, or the level of debridement and/or amputation necessary.¹² However, the bone biopsy does not come without pitfalls and limitations. A bone biopsy is an invasive procedure that may cause bacterial seeding in the presence of contaminated or infected soft tissue commonly present in diabetic foot ulcers.¹³

   Meyr and colleagues questioned the acceptance of this “gold standard.”¹ The authors performed a retrospective study, submitting 39 tissue specimens to four independent pathologists for analysis. All four pathologists diagnosed osteomyelitis in only 13 of 39 cases or 33 percent of the time. Is it possible the medical community has invested too much faith in the bone biopsy to confirm or exclude the presence of osteomyelitis?

Pertinent Insights On Less Invasive Imaging Modalities

A variety of less invasive imaging modalities can aid in diagnosing osteomyelitis. These modalities include plain radiographs, magnetic resonance imaging (MRI), computed tomography (CT) and nuclear medicine imaging. The modalities are useful in the early detection of osteomyelitis in order to prevent the further spread of infection and promote optimal patient outcomes with prompt intervention.¹⁴

   Despite all the advanced imaging options available, plain radiographs remain the preferred modality for the initial assessment of osteomyelitis. Plain radiographs are capable of differentiating infection from trauma or tumor, which all present with similar clinical findings.¹⁵ On the other hand, plain radiographs have a limited role in diagnosing acute osteomyelitis due to the “lag time” associated with radiolucency and cortical destruction.¹⁶ However, in the presence of chronic infection, defined as a bone infection present for more than 28 days, radiographic changes confirming the diagnosis of osteomyelitis are present 90 percent of the time.¹⁷ Therefore, despite all the emerging advances in the diagnosis of osteomyelitis, plain radiographs will remain relevant as an initial modality.