# Comparing the Diagnostic Accuracy of the Probe-to-Bone Test, Plain Radiography, and Serum Biomarkers in Detecting Diabetic Foot Osteomyelitis

## TL;DR

This study compares the accuracy of different tests for diagnosing bone infections in diabetic foot ulcers, finding that combining the probe-to-bone test with blood markers works as well as using imaging.

## Contribution

The study introduces the use of blood biomarkers as a diagnostic alternative to radiography in diabetic foot osteomyelitis.

## Key findings

- Combining PTB and biomarkers achieved 75% sensitivity and 24% specificity.
- PTB plus radiography had 76% sensitivity and 23% specificity.
- Biomarkers may be useful in areas with limited imaging access.

## Abstract

Background/Objectives: diabetic foot osteomyelitis (DFO) is a serious complication characterized by bone infection that can involve cortical structures, bone marrow, and surrounding soft tissues. Its prevalence ranges from 20% in moderate diabetic foot infections to over 50% in severe cases, making accurate diagnosis essential in guiding timely and effective management. in this study, we aimed to evaluate the diagnostic accuracy achieved by combining the probe-to-bone (PTB) test, plain radiography, and blood biomarkers—including the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)—in the diagnosis of DFO. Methods: we conducted a diagnostic accuracy study involving 128 patients with diabetic foot ulcers and clinical suspicion of DFO. The sensitivity, specificity, positive predictive value, and negative predictive value were calculated for individual tests and for their diagnostic combinations. Results: the combination of PTB and biomarkers yielded a sensitivity of 75%, a specificity of 24%, a positive predictive value of 69%, and a negative predictive value of 29%. Similarly, the combination of PTB and plain radiography showed a sensitivity of 76%, a specificity of 23%, a positive predictive value of 62%, and a negative predictive value of 38%. When the three diagnostic modalities were analyzed together, the sensitivity reached 75%, and the specificity reached 23%. Conclusions: the combination of PTB and inflammatory biomarkers demonstrated moderate effectiveness and diagnostic performance comparable to PTB combined with radiography. These findings suggest that biomarkers may serve as a practical and accessible diagnostic adjunct in settings where imaging availability is limited or radiographic interpretation is challenging.