CONTEXT: Osteomyelitis of the lower extremity is a commonly encountered problem 
in patients with diabetes and is an important cause of amputation and admission 
to the hospital. The diagnosis of lower limb osteomyelitis in patients with 
diabetes remains a challenge.
OBJECTIVE: To determine the accuracy of historical features, physical 
examination, and laboratory and basic radiographic testing. We searched for 
systematic reviews of magnetic resonance imaging (MRI) in the diagnosis of lower 
extremity osteomyelitis in patients with diabetes to compare its performance 
with the reference standard.
DATA SOURCES: MEDLINE search of English-language articles published between 1966 
and March 2007 related to osteomyelitis in patients with diabetes. Additional 
articles were identified through a hand search of references from retrieved 
articles, previous reviews, and polling experts.
STUDY SELECTION: Original studies were selected if they (1) described historical 
features, physical examination, laboratory investigations, or plain radiograph 
in the diagnosis of lower extremity osteomyelitis in patients with diabetes 
mellitus, (2) data could be extracted to construct 2 x 2 tables or had reported 
operating characteristics of the diagnostic measure, and (3) the diagnostic test 
was compared with a reference standard. Of 279 articles retrieved, 21 form the 
basis of this review. Data from a single high-quality meta-analysis were used to 
summarize the diagnostic characteristics of MRI in osteomyelitis.
DATA EXTRACTION: Two authors independently assigned each study a quality grade 
using previously published criteria and abstracted operating characteristic data 
using a standardized instrument.
DATA SYNTHESIS: The gold standard for diagnosis is bone biopsy. No studies were 
identified that addressed the utility of the history in the diagnosis of 
osteomyelitis. An ulcer area larger than 2 cm2 (positive likelihood ratio [LR], 
7.2; 95% confidence interval [CI], 1.1-49; negative LR, 0.48; 95% CI, 0.31-0.76) 
and a positive "probe-to-bone" test result (summary positive LR, 6.4; 95% CI, 
3.6-11; negative LR, 0.39; 95% CI, 0.20-0.76) were the best clinical findings. A 
erythrocyte sedimentation rate of more than 70 mm/h increases the probability of 
a diagnosis of osteomyelitis (summary LR, 11; 95% CI, 1.6-79). An abnormal plain 
radiograph doubles the odds of osteomyelitis (summary LR, 2.3; 95% CI, 1.6-3.3). 
A positive MRI result increases the likelihood of osteomyelitis (summary LR, 
3.8; 95% CI, 2.5-5.8). However, a normal MRI result makes osteomyelitis much 
less likely (summary LR, 0.14; 95% CI, 0.08-0.26). The overall accuracy (ie, the 
weighted average of the sensitivity and specificity) of the MRI is 89% (95% CI, 
83.0%-94.5%).
CONCLUSIONS: An ulcer area larger than 2 cm2, a positive probe-to-bone test 
result, an erythrocyte sedimentation rate of more than 70 mm/h, and an abnormal 
plain radiograph result are helpful in diagnosing the presence of lower 
extremity osteomyelitis in patients with diabetes. A negative MRI result makes 
the diagnosis much less likely when all of these findings are absent. No single 
historical feature or physical examination reliably excludes osteomyelitis. The 
diagnostic utility of a combination of findings is unknown.