BACKGROUND: We investigated the validity of probe-to-bone testing in the 
diagnosis of osteomyelitis in a selected subgroup of patients clinically 
suspected of having diabetic foot osteomyelitis.
METHODS: Between January 1, 2007, and December 31, 2008, inpatients and 
outpatients with a diabetic foot ulcer were prospectively evaluated, and those 
having a clinical diagnosis of foot infection and at least one of the 
osteomyelitis clinical suspicion criteria were consecutively included in this 
study.
RESULTS: Sixty-five patients met the inclusion criteria and were prospectively 
enrolled in the study. Forty-nine patients (75.4%) were hospitalized, and the 
remaining 16 (24.6%) were followed as outpatients. Osteomyelitis was diagnosed 
in 39 patients (60.0%). Probe-to-bone test results were positive in 30 patients 
(46.1%). The positive predictive value for the probe-to-bone test was fairly 
high (87%), but the negative predictive value was only 62%. The sensitivity and 
specificity of the test were 66% and 84%, respectively. White blood cell counts 
and mean C-reactive protein levels did not statistically significantly differ 
between groups. However, erythrocyte sedimentation rates greater than 70 mm/h 
reached statistical significance between groups. Wound area and depth were not 
found to be statistically significantly different between groups.
CONCLUSIONS: Positive probe-to-bone test results and erythrocyte sedimentation 
rates greater than 70 mm/h provide some support for the diagnosis of diabetic 
foot osteomyelitis, but it is not strong; magnetic resonance imaging or bone 
biopsy will probably be required in cases of doubt.