Except in the spine, labeled white-blood cell scintigraphy (WBCS) with image acquisition up to 24 h is the nuclear medicine test of choice for diagnosing osteoarticular infection. However, distinguishing between inflammation and infection is a challenge.Objectives
The first aim of this study was to verify earlier research studies that used 4 and 24 h time decay-corrected acquisition (TDCA) to differentiate infection from inflammation. The second aim was to analyze whether 8 h acquisition (1-day protocol) yielded similar results as 20–24 h acquisition.Patients and methods
This was an observational study of 94 patients (22–86 years, 52 women) with suspected osteoarticular infection referred to nuclear medicine to confirm infection. WBCS and TDCA images were obtained at 30 min, 4 h, and 8 h after injection of the labeled leukocytes, with collection times of 5, 8, and 12 min, respectively. Scintigrams were classified into three protocols: protocol 1: experts read only 30 min and 4 h images; protocol 2: experts read the whole set of images (30 min, 4 h, and 8 h) with different pixel intensities (each image normalized to its own maximum activity); protocol 3: experts read the whole set of images with the same pixel intensity. Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated. In patients with orthopedic implants, the interobserver reproducibility for visual analysis was calculated using the κ index.Results
Infection was confirmed in 26 cases. Sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and κ results were as follows: protocol 1: 92.3, 50.0, 41.4, 94.4, 61.7%, 0.79; protocol 2: 92.3, 94.1, 85.7, 97.0, 93.6%, 0.80; protocol 3: 96.2, 97.1, 92.6, 98.5, 96.8%, 0.77.Conclusion
TDCA acquisition of WBCS at 8 h (1-day protocol) enables a faster diagnosis than 24 h acquisition. The use of TDCA with the same pixel intensity in all images enables an accurate diagnostic of osteoarticular infection, with a considerable interobserver agreement for all protocols.