The value of serum TPHA titres in selecting patients for lumbar puncture.

Between January 1981 and December 1989, 258 patients with positive syphilis serology underwent lumbar puncture. Nine patients had long-standing neurosyphilis and had lumbar punctures performed during the course of their follow-up. Of the remaining 249 only 12 demonstrated the presence of TPHA in the CSF. The serum TPHA titre for eight of these 12 patients, and seven of the nine (two having no titre reported) known neurosyphilis patients at the time of original diagnosis, was 1 in 5120 or more. The four remaining newly found CSF positive patients had serum TPHA titres of 1 in 2560. We suggest that a serum TPHA titre of 1 in 2560 or greater should be considered as a criterion when selecting patients for lumbar puncture, especially when there are no clinical signs or symptoms.