Evaluation of white cell scintigraphy using indium-111 and technetium-99m labelled leucocytes

Indium-111 oxine labelled leucocyte (¹¹¹In oxine leucocyte) scintigraphy is the test of choice in detecting occult infection and localising focal inflammation. ¹¹¹In oxine labelling is technically difficult and expensive and leucocyte labelling with technetium-99m stannous colloid (^99mTc Sn colloid) has been considered to be an alternative. Leucocytes from 40 cases referred for investigation of occult infection or localisation of inflammation were simultaneously labelled with ¹¹¹In oxine and ^99mTc Sn colloid with dual isotope acquisition performed at 1, 3 and 24 h. Twenty-four hour ^99mTc Sn colloid scans were corrected for ¹¹¹In downscatter. Each case was independently interpreted by two experienced observers. Twentyone patients demonstrated positive ¹¹¹In oxine leucocyte scans. Using ¹¹¹In oxine leucocyte scans as the gold standard, ^99mTc Sn colloid leucocyte scanning had an overall sensitivity of 86% and a specificity of 95%. Clinical follow-up verified that three patients had false negative ^99mTc Sn colloid leucocyte scans and one patient had a false positive. Further clinical evaluation of ^99mTc Sn colloid labelled leucocytes is required before they can become a reliable replacement for ¹¹¹In oxine leucocytes. Correspondence to: S. Boyd