Intrathecal antitreponemal antibody synthesis determination using the INNO-LIA Syphilis Score

Laboratory detection of intrathecal synthesis of specific antitreponemal antibodies remains a challenge. Traditional syphilis serology is unable to provide a satisfactory result; therefore, several other diagnostic procedures were used to demonstrate central nervous system (CNS) involvement in this disease. The introduction of molecular methods makes today's laboratory testing easier.

Our study used a new commercially available test, the INNO-LIA Syphilis Score, intended for use on serum samples, to detect specific antitreponemal antibodies in the cerebrospinal fluid (CSF) of patients with the tertiary stage of syphilis.

We tested 26 patients suspected of neurological complications of late syphilis with conventional immunological tests such as VDRL-RPR, TPHA, FTA-ABS IgG, FTA-ABS-IgM, and the molecular INNO-LI Syphilis Score test for the presence of nontreponemal and treponemal antibodies. All tests were performed simultaneously in serum and CSF. The test results were evaluated with descriptive statistics and the probability was tested with an ANOVA test.

All 26 samples of serum were LIA-S (line immune assay in serum) positive and presented anticardiolipin and antitreponemal antibodies in high titer. Seventeen samples of CSF were LIA-L (line immune assay in liquor) positive and nine were LIA-L negative. Anticardiolipin and antitreponemal antibodies were detected only in the group of LIA-L positive samples. Anticardiolipin antibodies were present in two cases, antitreponemal (TPHA) in five cases, specific IgG (FTA-ABS IgG) in six cases, and specific IgM (FTA-ABS IgM) in one case. Six patients with antitreponemal antibodies in CSF presented with pathologic albumin index, two with a milder form, and four with a severe form. Two had a pathological IgG index and four a pathological IgM index. Altogether, two of the patients had laboratory signs of neurosyphilis.

Detecting anticardiolipin and antitreponemal antibodies in CSF in patients with a late form of syphilis is laborious. Using the new INNO-LIA Syphilis Score molecular test, we were able to identify patients with silent neurosyphilis together with patients with active intrathecal synthesis of IgG antibodies. The development of a new generation of tests for the detection of specific antitreponemal antibodies in CSF offers a valuable tool for discovering possible CNS involvement in syphilis.