Is the Combination of Plain X-ray and Probe-to-Bone Test Useful for Diagnosing Diabetic Foot Osteomyelitis? A Systematic Review and Meta-Analysis

A systematic review and meta-analysis was conducted to assess the diagnostic accuracy of the combination of plain X-ray and probe-to-bone (PTB) test for diagnosing diabetic foot osteomyelitis (DFO). This systematic review has been registered in PROSPERO (a prospective international register of systematic reviews; identification code CRD42023436757). A literature search was conducted for each test separately along with a third search for their combination. A total of 18 articles were found and divided into three groups for separate analysis and comparison. All selected studies were evaluated using STROBE guidelines to assess the quality of reporting for observational studies. Meta-DiSc software was used to analyze the collected data. Concerning the diagnostic accuracy variables for each case, the pooled sensitivity (SEN) was higher for the combination of PTB and plain X-ray [0.94 (PTB + X-ray) vs. 0.91 (PTB) vs. 0.76 (X-ray)], as was the diagnostic odds ratio (DOR) (82.212 (PTB + X-ray) vs. 57.444 (PTB) vs. 4.897 (X-ray)). The specificity (SPE) and positive likelihood ratio (LR+) were equally satisfactory for the diagnostic combination but somewhat lower than for PTB alone (SPE: 0.83 (PTB + X-ray) vs. 0.86 (PTB) vs. 0.76 (X-ray); LR+: 5.684 (PTB + X-ray) vs. 6.344 (PTB) vs. 1.969 (X-ray)). The combination of PTB and plain X-ray showed high diagnostic accuracy comparable to that of MRI and histopathology diagnosis (the gold standard), so it could be considered useful for the diagnosis of DFO. In addition, this diagnostic combination is accessible and inexpensive but requires training and experience to correctly interpret the results. Therefore, recommendations for this technique should be included in the context of specialized units with a high prevalence of DFO.