A cerebrospinal fluid test is needed to rule out neurosyphilis if the titer is still 1:16 after syphilis treatment. If the titer is still 1:16 after syphilis treatment, the possibility of neurosyphilis should be considered. After infection with syphilis, as long as through the standardized treatment of deworming, usually the antibody can be turned negative, but the time to turn negative varies from person to person, and some people may need a longer period of time to be able to turn negative. The non-specific antibodies produced by syphilis can be quantified by the titer of syphilis antibodies. The level of titer is directly related to the activity and infectiousness of syphilis and is proportional to it. A syphilis titer of 1:16 is very infectious in general, and requires a comprehensive evaluation by a professional doctor to consider whether to adjust the treatment plan. The majority of syphilis patients through standardized treatment, serum titer will gradually reduce, but some patients may drop to a certain level, the titer will not continue to decline, to be highly suspicious of the existence of neurosyphilis, need to do further cerebrospinal fluid examination to determine. If the titer is still 1:16 after syphilis treatment, further medical examination is needed to confirm the diagnosis.