SLR - November 2012 - Steve M Czymbor(2)
Reference: Erdman WA, Buethe J, Bhore R, Ghayee HK, Thompson C, Maewal P, Anderson J, Klemow S, Oz OK. (2012) Indexing Severity of Diabetic Foot Infection with 99mTc-WBC SPECT/CT Hybrid Imaging. Diabetes Care, 35 (9), 1826-1831. DOI:10.2337/dc11-2425/-/DC1.
Scientific Literature Review
Reviewed by: Steve M. Czymbor, DPM
Residency Program: Columbia St. Mary’s, Milwaukee, WI
Podiatric Relevance:
Assessing the severity of a diabetic foot infection can be difficult with standard imaging techniques as infectious processes can be masked by degenerative and reparative changes unrelated to the infection. Currently, MRI is the imaging procedure of choice but is of low specificity at times such as with previous surgeries or degenerative changes when evaluating for infection. Radiolabeled WBC SPECT/CT is a newer imaging modality that can help guide treatment in a diabetic foot infection.
Methods:
Diabetic patients with a suspected diabetic foot infection were retrospectively reviewed, 101feet in total. All patients were followed at least three months from initiation of therapy. SPECT/CT images with one-mm slices were obtained on all feet two hours after injection of 99mTc-WBC. Images were then reviewed at separate times and ranked by a composite severity index and a binary osteomyelitis, no osteomyelitis grading system. Composite severity index (CSI) included grading for intensity of WBC focus as well as the progression of WBC infiltration. Patients were also broken into categories of receiving antibiotic treatment greater than or less than 42 days if they did or did not have osteomyelitis, respectively.
Results:
Out of the 101 feet initially reviewed, 77 were technically accurate for this study. CSI was statistically more accurate than the conventional binary interpretation method when predicting therapeutic outcome. The proposed prognostic algorithm was most sensitive with composite scores of less than two, with specificity greater than or equal to 90 percent for scores of seven or greater. Using logistic regression, one could more accurately determine efficacy of antibiotic treatment duration as opposed to the binary osteomyelitis, no osteomyelitis system.
Conclusions:
Dual modality SPECT/CT scanners can be used to help guide treatment algorithms in diabetic foot infections, increasing specificity of osteomyelitis in certain instances. There was no benefit to prolonged antibiotic therapy (greater than 42 days) in patients with a CSI of seven or greater. Patients with CSI scores between three and six were almost twice as likely to benefit from a prolonged antibiotic course of six weeks or greater.