Format

Send to

Choose Destination
Sex Health. 2012 Nov;9(5):488-90. doi: 10.1071/SH11156.

Case report and evaluation of the frequency of the prozone phenomenon in syphilis serology - an infrequent but important laboratory phenomenon.

Author information

1
Department of Infectious Diseases, Prince of Wales Hospital, Randwick, Australia. Jeffrey.Post@sesiahs.health.nsw.gov.au

Abstract

BACKGROUND:

Treponema pallidum specific serology generally remains reactive for life. Therefore, the diagnosis of syphilis reinfection relies on clinical assessment and nontreponemal (reagin) serologic testing. The prozone phenomenon can lead to a falsely nonreactive rapid plasma reagin (RPR) assay result.

METHODS:

We report a case of secondary syphilis in a HIV infected patient with a previous history of syphilis infection, where a falsely nonreactive RPR assay was associated with a delayed diagnosis of reinfection and infectious syphilis. The prozone phenomenon was detected in several of the patient's serum samples collected around this time. We subsequently undertook a prospective evaluation for the prozone phenomenon in 3222 consecutive sera, which were assayed using the RPR assay for clinical purposes over a 10-month period.

RESULTS:

The overall rate of the prozone phenomenon was 2 out of 3222 samples (0.06%; 95% confidence interval (CI): 0.02-0.22%) and the rate per reactive sample was 2 out of 397 (0.5%; 95% CI: 0.14-1.81%).

CONCLUSION:

Clinicians should request RPR testing at dilutions of sera when syphilis is suspected clinically and the RPR assay is nonreactive.

PMID:
22958508
DOI:
10.1071/SH11156
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for CSIRO
Loading ...
Support Center