Utility of 8 h and time decay-corrected acquisition scintigraphy with in-vitro labeled white blood cells for the diagnosis of osteoarticular infection.

INTRODUCTION: 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.

Succinylated gelatine: an alternative to hydroxyethyl starch for labelling leukocytes with 99mTc-HMPAO.

BACKGROUND: Hydroxyethyl starch (HES) is the most used plasma expander in the sedimentation of the erythrocytes during the radiolabelling procedure for leukocytes in vitro. AIM: To evaluate the usefulness of succinylated gelatine (GEL), another colloidal plasma expander, as an alternative to HES in this process. METHODS: Two identical blood samples were obtained from 30 patients referred to white blood cell scintigraphy. The first sample was used to label leukocytes with Tc-HMPAO using the routine procedure, with HES. The other sample was used to label leukocytes with Tc-HMPAO using the same procedure, with GEL. The cell concentration of the leukocyte-platelet-rich plasma (LPRP) achieved after blood sedimentation was analysed. Labelling efficiency was calculated and the eosin Y viability and red cell/leukocyte ratio were evaluated from the final labelled cell suspension. RESULTS: Leukocytes and platelets recovered in LPRP were not statistically different between both HES and GEL samples (leukocytes: 8.10x10/microl+/-3.82 and 7.80x10/microl+/-3.47; platelets: 411x10/microl+/-182 and 406x10/microl+/-172, respectively). There were no significant differences between both agents on the labelling efficiency (HES: 80.3%+/-6.6%; GEL: 80.1%+/-6.3%), the eosin Y viability (HES: 99.2%+/-1.3%; GEL: 99.3%+/-1.1%) and the red cell/leukocyte ratio (HES: 1.21+/-0.7; GEL: 0.9+/-0.5). CONCLUSION: These results show that succinylated gelatine can be used instead of hydroxyethyl starch in the labelling of leukocytes with Tc-HMPAO.