Syphilis – Chancre – Direct Fluorescence

Testing Indications

Direct fluorescence for detection of Treponema pallidum is indicated for the diagnosis of primary or secondary syphilis from suspected chancre or lesions.

Limitations

A swab received in charcoal or antibiotic transport medium is not an acceptable specimen. If smears are prepared too thick or show signs of gross contamination with blood, they are unacceptable and the sample will not be tested. Submitter will be notified by telephone.

Due to the low sensitivity of the test, a blood sample should always be submitted for syphilis serology testing when syphilis is suspected.

Storage and Transport

Label slide with the patient’s full name and date of birth. Allow slide to dry and put it in slide mailer provided with the kit and place in a biohazard bag and seal. Failure to provide this information may result in rejection or testing delay.

Special Instructions

Specimens should be stored at 2-8 °C following collection and shipped to the Public Health Ontario Laboratory for testing. Avoid extreme temperature.

Test Frequency and Turnaround Time (TAT)

Direct fluorescence for syphilis is performed 2-3 times per week. 

Turnaround time is up to 2 days from receipt by PHO laboratory.

Smears from lesions or chancres for syphilis are tested by direct fluorescence.

The syphilis test detects spirochetes by fluorescent microscopy, however, due to the low sensitivity of the test, a negative result does not rule out syphilis.

Reporting

Results are reported to the ordering physician or health care provider as indicated on the requisition.

Specimens that are positive for syphilis are reported to the Medical Officer of Health as per Health Protection and Promotion Act. 

References

LAB-SD-057, Syphilis (Treponema pallidum) Serology Testing and Interpretation - Update