Quadruple ("Quad") Screen

…is a blood test at 16-20 weeks which looks for four different types of proteins. It is a triple screen with the addition of Dimeric Inhibin-A, another placental protein, and was globally first introduced in 1996. It gives a detection rate of 72-75%, with 5% false positives, and this means that 25-28% of affected pregnancies are missed by this test.

SIPS

…is short for "Serum Integrated Pregnancy Screening". It involves taking blood in the first trimester (12 weeks) for PAPP-A determination, and then adding in a quadruple screen in the second trimester (16-20 weeks) giving a final result after the quadruple screen. It performs at a 82-84% detection rate for 5% false positives, and is an improvement on the quadruple screen. This means that 16-18% of affected pregnancies are missed by this test. Note that the PAPP-A measurement is not disclosed to the patient or the doctor, until the quadruple screen is completed.

IPS

…stands for "Integrated Pregnancy Screening". IPS involves adding a Nuchal Translucency (the 12 week ultrasound test for looking at the fetal neck), and adding to it the SIPS. This gives a final answer at the end of the quadruple screen (17-20 weeks). In BC, IPS is performed as a sequential test: this means that the NT is performed at 12 weeks, and if the NT is large, the patient is offered amniocentesis, or they can wait for the rest of the blood work in later pregnancy. This type of sequential testing performs at a 88% detection rate and is inferior to FTS (NT, Nasal Bone, and First trimester bloodwork). This means that 12% of affected pregnancies are missed by this test. In BC, IPS is offered currently to women over age 40, HIV positive, and patients with twins. This is likely to change in the near future.

In its pure form, IPS is sometimes (not in BC) performed as a ‘combined’ test, meaning that the first and second trimester blood and ultrasound results are not disclosed to the patient, until completion of the second trimester bloodwork.  In this form, IPS performs very similar to FTS in detection rates. However, it is very hard not to disclose the results of the ultrasound to a patient without a lot of patient anxiety. For this reason, combined IPS is not popular.

If FTS with Nasal Bone performs so well, why isn’t it widely offered?

It is widely offered. Screening programs in Ontario and Alberta utilize FTS with nasal bone. 45 countries now perform FTS as part of nationalized programs. The UK has recently de-insured quadruple screening. The problem is largely in training, and political motivation to change the current standards. With NT, Nasal Bone, DV and first trimester serum (hCG and PAPP-A), the test has a detection rate of 96%. This means that 4% of affected pregnancies are missed by this test.