Our objective is to assess the specificity and sensitivity, and thus elabor
ate the relevance, of different laboratory findings for the diagnosis of ne
urosyphilis.
One hundred and fourteen HIV-negative pairs of serum and cerebrospinal flui
d (CSF) samples were examined by the Venereal Disease Research Laboratory (
VDRL) test, a fluorescent treponemal antibody-absorption (FTA-ABS) test, mi
crohaemagglutination assay with Treponema pallidum antigen (MHA-TP) test (s
erum) and Treponema pallidum haemagglutination assay (TPHA) test (CSF); fur
ther, albumin, total protein, and total IgG were determined and, in the CSF
, cell count was performed. The donors were 60 patients with active neurosy
philis and 54 healthy persons with a former history of syphilis and with pe
rsisting positive results in the T. pallidum haemagglutination tests (serum
: MHA-TP, CSF: TPHA), who supplied specimens for control. Albumin quotient,
IgG index, TPHA index, modified TPHA index, Intrathecally produced T. pall
idum Antigen (ITpA) index, its 2 modifications and, in 12 samples, the aden
ovirus group antibody (AVGA)/TPHA index were ascertained.
The specificity and sensitivity of the TPHA index were 100% and 98.3%, of t
he modified TPHA index 50.0% and 96.7%, of the ITpA index 42.6% and 90.0%,
of the modified ITpA indices 51.8% and 68.3% (first modification) and 53.7%
and 63.3% (second modification). The AVGA/TPHA index yielded a specificity
of 91.7% (11/12). The CSF VDRL test was positive in 55/60 (91.7%) of sampl
es from patients with neurosyphilis and in none of the controls (0/54). A C
SF-TPHA titre greater than 1:320 was observed in 59/60 (98.3%) of the neuro
syphilis specimens and in none of the controls (0/54).
A TPHA index above an outcome of 70, a positive CSF-TPHA test at a titre gr
eater than 1:320 and, with lower sensitivity, the criteria of the Centers f
or Disease Control (CDC) guidelines yield the most reliable results for lab
oratory support to a diagnosis of neurosyphilis. The modified TPHA index, t
he ITpA index, and its 2 modifications produce results of minor sensitivity
and poor specificity. Observations on the AVGA/THPA index are too limited
yet for judgement. The diagnostic significance of a CSF-TPHA titre above 32
0 needs further confirmation on a greater number of observations made by di
fferent laboratories.