The technetium-99m DTPA partition test in the diagnosis of tuberculous meningitis.

Although the blood/cerebrospinal fluid (CSF) bromide concentration ratio is sensitive and specific in the diagnosis of tuberculous meningitis (TBM), bromide-82 is not always available since it is not generally used in nuclear medicine. The use of technetium-99m diethylenetriamine penta-acetic acid (DTPA) for a partition test was compared with that of 82Br in 22 cases. Seven patients were diagnosed as having TBM, 9 patients had viral meningitis and 5 patients had septic meningitis. One normal control subject was also studied. Although the mechanism of transfer of substances across the blood-brain barrier as well as the factors affecting it are still unclear, both 82Br and 99mTc-DTPA cross the blood-brain barrier to a greater extent in TBM than in viral meningitis. Both tracers thus yield decreased serum/CSF concentration ratios in TBM. The accuracy of the 82Br partition test was found to be 90,9% if a critical serum/CSF ratio of 1,3 was chosen, compared with 86,9% for the 99mTc-DTPA partition test if a critical value of 3 was chosen. The use of 99mTc-DTPA offers various advantages, including general availability, lower cost and radiation dose per MBq, as well as the possibility of concomitant brain scintigraphy.