Usefulness of Procalcitonin in Diagnosing Diabetic Foot Osteomyelitis

A Pilot Study

Venkat N. Vangaveti, PhD; Oliver G. Heyes, MD; Shaurya Jhamb, MD; Nagaraja Haleagrahara, PhD; Usman H. Malabu, MD, FACP, FRACP

Disclosures

Wounds. 2021;33(7):192-196. 

In This Article

Discussion

Diabetic foot ulcers are of major concern among patients with long-term diabetes mellitus. Most diabetic foot infections are diagnosed based on clinical findings and may need invasive tests to confirm DFO.[12] Therefore, a suitable diagnostic marker with a high clinical utility, high sensitivity (true positive correctly identified by a test), and sensitivity (true negative correctly identified by a test) would be useful to confirm the diagnosis, rationalize requirement for invasive testing, and prevent delays in modified treatment regimens due to delay in diagnosis. The current study demonstrated significantly high levels of PCT and IL-6 in the DFO group compared with the control group. Procalcitonin has been proposed as an ideal candidate for diagnosing diabetic foot infection; the serum level of PCT has been shown to be elevated in diabetic foot infections, as reviewed by Velissaris et al.[13] Similar to the present study, Uzun et al[14] reported a significant difference in levels of PCT in patients with DFO, with a sensitivity and specificity of 77% and 100%, respectively, at the cutoff value of PCT greater than or equal to 0.08 ng/ml and 0.06 ng/ml. The authors also reported comparable sensitivity and specificity as in the present study. Similarly, a significant difference in levels of PCT was found in patients with infected foot ulcer compared with non-infected foot ulcer with high specificity (100%) and a sensitivity of 23.3%,[15] although it is unclear from the study if the infected foot ulcers were confirmed to have DFO or cellulitis without bone infection. On the other hand, Asirvatham et al[16] found PCT to have a high sensitivity and specificity of 80% and 75%, respectively, in diagnosing DFO at a serum level of 60.0 pg/mL, very similar to the findings in the present study.

In contrast to the above findings, Korkmaz et al[17] did not report elevated levels of PCT in patients with DFO. Interestingly, the present study also showed increased levels of IL-6 levels in patients with DFO, as previously reported by others.[18] This study showed MLR to be a candidate for predicting osteomyelitis at a cutoff point of 0.3, with a sensitivity and specificity of 74% and 67%, respectively, and a fair test based on clinical utility index. This study did not observe PLR to have good utility, unlike the study reported by Demirdal et al.[19]

The present study suggests PCT and IL-6 could be practical diagnostic tests for differentiating DFO from cellulitis based on clinical utility index. The cost of the PCT test works out to be approximately $20 per test compared with performing a bone scan or an MRI at a cost of about $270 in Australia.[3] A preliminary test for PCT would be beneficial and could be conducted before an MRI or bone scan to confirm the findings. This is particularly relevant for patients in resource-deprived and/or economically developing countries or those from rural and remote areas in economically developed countries who would not have to travel to a tertiary hospital in urban areas to undergo an MRI or a bone scan to confirm the DFO diagnosis. Additionally, preliminary testing may also help save costs to the health care provider.

It is important to note that the present study is, to the authors' knowledge, the first study in patients with DFO compared with non-DFO with cellulitis. Previous studies demonstrated differences in serum levels of PCT between DFO and diabetic non-infected foot controls.[16,17] The present results faced potential limitations, including small sample size, though they fitted with the outlined objectives of a pilot study. Secondly, a bone biopsy was not conducted on all patients involved in the study. Although bone biopsy is usually considered a gold standard for the diagnosis of osteomyelitis, such a procedure may not be routinely performed in clinical practice due to ethical issues of creating a new wound by excising adjacent healthy tissue and worsening the healing process, particularly in patients with a low index of suspicion for DFO. Instead, the authors used the recommendation of the International Working Group on the Diabetic Foot in defining DFO in this study.[12] Also, a detailed study would be needed to understand the impact of ischemia and dialysis on the biomarkers as indicator for osteomyelitis, as this cohort has a higher risk for amputation. Despite these, the present results are consistent with others' findings of the diagnostic usefulness of PCT in DFO.[16,17]

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