Are ESR (Erythrocyte Sedimentation Rate) and CRP (C-Reactive Protein) useful for evaluating diabetic osteomyelitis?

From the Guidelines

ESR and CRP are useful but limited markers for evaluating diabetic osteomyelitis, and should be used in combination with other diagnostic tools, such as clinical findings, imaging studies, and bone culture results, as recommended by the most recent guidelines 1. When evaluating diabetic osteomyelitis, it is essential to consider the limitations of ESR and CRP as standalone diagnostic tools. Both are non-specific inflammatory markers that can be elevated in various conditions, including infections, inflammatory diseases, and even non-infectious processes.

• CRP tends to be more sensitive and responds more quickly to inflammation, rising within 6-8 hours and peaking at 48 hours, while ESR rises more slowly, peaking at 3-5 days, and can remain elevated for weeks even after successful treatment 1.
• A declining CRP is generally a more reliable early indicator of improvement than ESR when monitoring treatment response.
• Normal values of ESR and CRP do not exclude osteomyelitis, particularly in immunocompromised patients, and mildly elevated values do not confirm it.
• The most recent guidelines recommend using a combination of diagnostic tools, including probe-to-bone test, plain X-rays, and ESR or CRP, as initial studies to diagnose osteomyelitis of the foot in patients with diabetes 1.
• MRI is the preferred imaging modality for diagnosing diabetic foot osteomyelitis, and should be used when the diagnosis remains in doubt despite clinical, plain X-rays, and laboratory findings 1.

From the Research

Diagnostic Value of ESR and CRP in Diabetic Osteomyelitis

• ESR and CRP are commonly used inflammatory markers to evaluate diabetic osteomyelitis 2, 3, 4, 5, 6.
• Studies have shown that ESR and CRP levels are significantly higher in patients with osteomyelitis compared to those with soft-tissue infections 2, 3, 4, 5, 6.
• The optimal cutoff values for ESR and CRP to diagnose osteomyelitis have been determined to be around 60 mm/h and 7.9 mg/dL, respectively 3.
• ESR has been found to be better for ruling out osteomyelitis initially, while CRP helps distinguish osteomyelitis from soft-tissue infection in patients with high ESR values 3.
• The diagnostic accuracy of ESR and CRP has been reported to be fair and poor, respectively, in detecting diabetic foot osteomyelitis 4.
• Other studies have found that the CRP:albumin ratio is a useful marker for detecting osteomyelitis in patients with diabetic foot ulcers, with a cutoff value of 1.74 or above having a sensitivity of 92.0% and specificity of 80.9% 5.
• Procalcitonin has also been found to be a useful marker for diagnosing osteomyelitis in diabetic foot patients, with a sensitivity of 100% and specificity of 97.8% 6.

Clinical Applications

• ESR and CRP can be used as diagnostic markers for osteomyelitis in diabetic patients, but their accuracy may vary depending on the cutoff values used 2, 3, 4.
• The CRP:albumin ratio may be a useful additional marker for detecting osteomyelitis in patients with diabetic foot ulcers 5.
• Procalcitonin may be a useful marker for diagnosing osteomyelitis in diabetic foot patients, especially when used in combination with other diagnostic tests such as MRI or bone biopsy 6.

Limitations

• The diagnostic accuracy of ESR and CRP may be limited by various factors, such as the presence of comorbidities or other infections 2, 3, 4.
• Further studies are needed to determine the optimal cutoff values for ESR and CRP in different patient populations and to evaluate the clinical utility of these markers in diagnosing osteomyelitis 2, 3, 4.