Reliability of white blood cell scan in the follow-up of osteomyelitis.

INTRODUCTION: The question of whether antibiotic treatment does or does not affect reliability of white blood cell scan (WBCS) to detect disease activity in clinical practice is still unanswered. Our aim was to study the relationship between scintigraphic findings of WBCS and antibiotic therapy in a group of patients affected with osteomyelitis (OM). METHODS: We retrospectively reviewed 57 scans, performed in 18 patients affected by OM and who were on antibiotic treatment. The number of therapy weeks was calculated for each antibiotic. A comparison of results obtained during and after discontinuation of the antibiotic treatment was made. Overall sensitivity, specificity and accuracy of WBCS were calculated and compared with those obtained in patients undergoing therapy. RESULTS: Forty-seven scans were performed during treatment and 10 scans after discontinuation of treatment. The scintigraphic results obtained during and after discontinuation of treatment were as follows: TN 14 and 8, TP 31 and 2, FN 2 and 0, FP 0 and 0, respectively. Sensitivity, specificity and accuracy of WBCS, calculated in all patients, were 94.3%, 100% and 96.5% respectively. In patients receiving antibiotic therapy, the same parameters were 93.9%, 100% and 95.7% respectively. In patients treated with antibiotics that can decrease leukocyte function, there were 10 TN, 14 TP, 2 FN and 0 FP, while in patients treated with antibiotics that have not effect on leukocyte function there were 4 TN, 17 TP, 0 FN and 0 FP. CONCLUSION: The reliability of WBCS in the detection of disease activity during antibiotic treatment does not change significantly. It can be assumed that the influence of antibiotic therapy on labelled leukocyte behaviour is negligible.

White blood cell scintigraphy in the diagnosis of infection of endovascular prostheses within the first month after implantation.

BACKGROUND: 99mTc-HMPAO-labeled leukocyte scintigraphy (WBCs) is useful in the diagnosis of vascular graft infection. However, false positives can occur in the early postoperative period. There are no data concerning the usefulness of WBCs in detecting endovascular prosthesis infection during this period. The aim of our study was to assess the reliability of WBCs in the diagnosis of early infection after endovascular prosthesis implantation. MATERIAL/METHODS: 23 patients treated with endovascular grafts were submitted to preoperative diagnostic screening and to 3 WBCs (1 week before, 1 week after, and 1 month after surgery). After the last WBCs, all patients underwent a 14-month follow-up (range 6-37 months, median 12 months). RESULTS: Three patients died, at 3, 4 and 5 months after surgery respectively. At the end of the follow-up, the presence of infection was demonstrated in one patient. Of the 70 WBCs performed, 4 gave positive results. No positive scintigraphies were obtained in the preoperative period. A positive scintigraphy was found one week after surgery in a patient who showed lymphorrhage at the site of surgical access. In the same patient, the scintigraphic result returned to normal at 1-month scintigraphy. At 12-month follow-up the patient did not present signs of infection. Three positive scintigraphies were obtained in the same patient. In this patient clinical symptoms of graft infection became evident about 19 months after surgery. WBCs was repeated and showed extension of the infection. The infection was confirmed at surgery. CONCLUSIONS: WBCs do not provide false-positives in the first month after endovascular prosthesis implantation.

The effects of 99mTc-HMPAO-labelled leucocyte scan on human karyotype.

Technetium-99m hexamethylpropylene amine oxime (HMPAO) white blood cell scan (WBCS) requires separation and labelling of mixed leucocytes, which include particularly radiosensitive cells, lymphocytes. Lymphocytes labelled during the mixed leucocyte labelling procedure could represent a problem for patients owing to the possible induction of chromosomal aberrations. Lymphocytes labelled in mixed leucocyte preparations are probably killed by the high-dose radiation. Nevertheless, it has been reported that some of these lymphocytes can proliferate after in vitro stimulation. If these cells were to reproduce themselves in vivo, onset of, or increase over time in, chromosomal aberrations could occur on peripheral blood lymphocytes. The present study was performed on 21 patients who underwent WBCS for suspected infection/inflammation. Blood samples of these patients were submitted to cytogenetic study, comprising karyotype determination, evaluation of sister chromatid exchanges (SCE) and evaluation of induced chromosomal breakages or rearrangement rate (B/R). This study was performed 2 h before and 7 days and 6 months after the WBCS. The results demonstrated no statistically significant differences between SCE and B/R values before and after WBCS. No cause-effect relationship appeared to exist between WBCS and the onset of chromosomal aberrations in peripheral blood lymphocytes, at least during the first 6 months post WBCS and within the limits of this study's approach. The high-dose radiation administered to lymphocytes was almost certainly sufficient to kill these cells.