Prenatal – Serology

Testing Indications

All pregnant women should be screened for HIV, SYPHILIS, RUBELLA and HEPATITIS B SURFACE ANTIGEN (HBsAg). Testing for hepatitis B immunity (HBsAb) is not required for prenatal screening and will be rejected unless a clear reason for testing (e.g. exposure to a case, needlestick injury, etc.) is indicated on the requisition.

In Ontario, it is recommended that all pregnant women be offered HIV testing regardless of their apparent risk. Testing is recommended with each pregnancy, regardless of previous screening, as infection may have occurred in the interim.

Limitations

Haemolysed, icteric, lipemic or microbially contaminated sera is not recommended for testing.

Storage and Transport

Label the specimen container with the patient’s full name, date of collection and one other unique identifier such as the patient’s date of birth or Health Card Number. Failure to provide this information may result in rejection or testing delay.

Centrifuge if using SST. Place specimen in biohazard bag and seal. Specimens should be stored at 2-8°C following collection and shipped to PHO’s laboratory on ice packs within 3 days of collection. Specimens more than 6 days post collection will not be tested. If delayed shipping is anticipated, remove serum from clot and store frozen at -20°C or colder and ship on dry ice.

Special Instructions

Indicate the prenatal screen test requested by checking the box(es) in Section 3 – Test(s) Requested of the Prenatal Screening Requisition. If the patient is being screened for HIV and has risk factors for HIV, please also complete and submit the HIV Serology Requisition.

Test Frequency and Turnaround Time (TAT)

Rubella - Serology testing is performed daily Monday to Friday. Turnaround time is up to 5 days from receipt by PHO’s laboratory.

Syphilis – Serology screen testing is performed daily Monday to Friday. Turnaround time is up to 3 days from receipt by PHO’s laboratory for non-reactive samples and up to 6 days for reactive samples.

HIV and HBsAg - Serology testing is performed daily Monday to Friday. Turnaround time is up to 3 days from receipt by PHO’s laboratory for non-reactive samples and up to 6 days for reactive samples.

Hepatitis B Surface Antigen (HBsAg): Pregnant in labor with no prenatal work up and high risk for Hepatitis B.

HIV: Pregnant in labor with no prenatal work up and high risk for HIV.

“STAT” specimens must be shipped separately from routine specimens in a clearly marked package indicating “STAT” and handled in accordance with the Canadian Biosafety Standards, and shipped in accordance with the Transportation of Dangerous Goods Regulations. Failure to ship separately will delay testing.

Prenatal screening serology is performed using a chemiluminescent microparticle immunoassay (CMIA) for the qualitative detection of the respective markers in human serum.

Algorithm

RUBELLA: refer to the Rubella – Serology Test Information Sheet 
SYPHILIS: refer to the Syphilis – Serology Test Information Sheet
HIV: refer to the HIV – Diagnostic Serology Test Information Sheet
HEPATITS B SURFACE ANTIGEN (HBsAg): if HBsAg is reactive, further testing for anti-HBV core (anti-HBc Total) antibody and/or HBsAg confirmatory testing is performed.

Interpretation

Results are reported as reactive or non-reactive. Please refer to the Test Information Sheets above for specific interpretations.

Reporting

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

Specimens that are positive for syphilis, HIV, and/or Hepatitis B surface antigen (HBsAg) are reported to the Medical Officer of Health as per Health Protection and Promotion Act.

References

LAB-SD-008, Blood Collection using Serum Separator Tubes

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