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

Abstract

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.

Keywords: diabetic foot; diabetic foot osteomyelitis; diabetic foot ulcer; plain X-ray; probe-to-bone test.

Figure 1

Flowchart of identified studies.

Figure 2

PTB’s pooled sensitivity and specificity compared to histopathology [12,13,16,23]. TP, true positive; FN, false negative; TN, true negative; FP, false positive; CI, confidence interval.

Figure 3

ROC curve and extracted statistical variables of PTB–Histopathology studies. LR+, positive likelihood ratio; I², heterogeneity; AUC 95%, 95% confidence interval of the area under the curve; DOR, diagnostic odds ratio.

Figure 4

Plain X-ray’s pooled sensitivity and specificity compared to histopathology [13,16,25,27,30,31,33]. TP, true positive; FN, false negative; TN, true negative; FP, false positive; CI, confidence interval.

Figure 5

ROC curve and extracted statistical variables of plain X-ray and histopathology studies. LR+, positive likelihood ratio; I², heterogeneity; AUC 95%, 95% confidence interval of the area under the curve; DOR, diagnostic odds ratio.

Figure 6

Extracted statistical variables of the combination of PTB + plain X-ray. LR+, positive likelihood ratio; I² SEN, sensitivity heterogeneity; I² SPE, specificity heterogeneity; DOR, diagnostic odds ratio.

Figure 7

Combined tests’ sensitivity and specificity pools compared to histopathology [13,16]. TP, true positive; FN, false negative; TN, true negative; FP, false positive; CI, confidence interval.