Immunoscintigraphy of the bone marrow: normal uptake values of technetium-99m-labeled monoclonal antigranulocyte antibodies.

UNLABELLED

The aim of our study was to determine the normal range of the 99mTc-labeled anti-NCA 95 antigranulocyte antibody (AGAb) uptake in the bone marrow using the sacroiliac-to-background uptake ratio in the posterior view.

METHODS

We made 169 planar bone marrow scans on 162 patients who were each injected with 555 MBq AGAb. Fifty patients with the diagnosis of infection/pyrexia of unknown origin (PUO) and with completely normal bone marrow scintigraphy were defined as the normal group. Uptake ratios were calculated drawing irregular regions of interest around the sacroiliac and a background area, respectively.

RESULTS

The normal group revealed a mean uptake ratio of 7.3 +/- 2.3 (range 4.4-12.6). Similar uptake ratios were obtained in patients with the primary diagnosis of infection/PUO and bone marrow extension (7.4 +/- 2.2, range 4.2-11.7), suggesting that the bone marrow reacts on infection primarily by extension into the periphery, without any significant increase of the activity of the central hemopoietic/granulopoietic bone marrow. Mean uptake ratios also were not significantly different in patients with normal bone marrow scintigraphy and the primary diagnosis of solid malignant tumors, lymphomas and plasmacytomas, and in patients with focal lesions visible on bone marrow scintigraphy (soft tissue inflammation or cold lesions in the bone marrow but with normal sacroiliac regions). Mean uptake ratios in the normal group were significantly age related, amounting to 8.5 +/- 1.8, 7.5 +/- 1.9 and 6.1 +/- 2.0 in patients younger than 40 yr, between 40 and 59 yr, and 60 yr or older, respectively (p = 0.0025). The method revealed good inter- and intraobserver agreement with correlation coefficients of about r = 0.90 and r = 0.95, respectively. Inter- and intraobserver coefficients of variation were 6.6% and 4.6%, respectively.

CONCLUSION

Determination of the bone marrow uptake ratio is simple and reproducible. The normal values established in this study were age dependent, which has to be considered when interpreting bone marrow uptake ratios. The presence of infection/PUO, solid malignant tumors, lymphomas and plasmacytomas does not seem to alter the AGAb uptake ratio significantly. The most important application of the quantitative analysis of bone marrow scintigraphy could be the diagnosis and follow-up of diseases with depression of the central hemopoietic activity.