Diagnosis of infected total knee arthroplasty with anti-granulocyte scintigraphy: the importance of a dual-time acquisition protocol.
OBJECTIVE
To evaluate clinical efficacy of a dual-time acquisition protocol consisting of early 4 h and delayed 20-24 h imaging with anti-granulocyte scintigraphy (LeukoScan) in the diagnosis of infection in painful total knee arthroplasty (TKA).


METHODS
Seventy-eight consecutive patients with TKA (12 bilateral) were prospectively enrolled in the study from August 2004 to July 2005. All the patients had clinical and biochemical suspicious of infection, except for the 12 patients with bilateral painless prosthesis who had no signs and symptoms of loosening and/or infection and were considered as controls. TKA prostheses had been implanted 4 months to 9.5 years before our studies. Forty-three patients were on antibiotic therapy at the moment of scintigraphic examination, and treatment was not discontinued. All patients underwent LeukoScan examination by performing both early 4 h and delayed 20-24 h imaging. In addition to planar imaging SPECT was performed in 18 cases. A decrease in radiotracer uptake from early to delayed LeukoScan imaging was interpreted as an unspecific finding (negative for infection), while an increasing uptake was interpreted as a positive finding for the presence of infection. Three-phase Tc-MDP bone scan was also routinely performed by standard technique. Sensitivity and specificity of early and delayed LeukoScan imaging were calculated.


RESULTS
Sensitivity for early and delayed imaging were 92.7%, while specificity was 78.4% for early imaging and 100% for delayed imaging approach. SPECT imaging did not add any significant information as regard to specificity in our experience. Eight false positive early scans were correctly diagnosed as negative at delayed imaging. Three false negative results were recorded. Sensitivity and specificity were similar when patients were on or off antibiotic therapy. Imaging was negative in all 12 controls.


CONCLUSIONS
Our results, based on a large group of patients, suggest that delayed LeukoScan imaging is important in identifying false positive results detect at early imaging. Thus, a dual-time, 4 h early and 20-24 h delayed LeukoScan imaging approach should be recommended to increase the diagnostic accuracy of the scintigraphy, with the exception of patients with a negative early LeukoScan examination, in whom the acquisition of delayed imaging appears unnecessary. In our experience, concomitant antibiotic therapy did not influence the diagnostic value of LeukoScan.
Rubello
Domenico
D
Service of Nuclear Medicine - PET Unit, 'S. Maria della Misericordia' Hospital, Istituto Oncologico Veneto (IOV) - IRCCS, Viale Tre Martiri, Rovigo, Italy. domenico.rubello@libero.it
Rampin
Lucia
L
Banti
Elena
E
Massaro
Arianna
A
Cittadin
Silvia
S
Cattelan
Anna Maria
AM
Al-Nahhas
Adil
A
D000368:Aged; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D001168:Arthritis / Q000000981:diagnostic imaging* / Q000209:etiology; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D016459:Prosthesis-Related Infections / Q000000981:diagnostic imaging* / Q000209:etiology*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors
D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D019275:Radiopharmaceuticals; C101172:Sulesomab