Tag Archives: CAPILLARY BLOOD COLLECTION

HDN DUE TO RHESUS INCOMPATIBILITY


Rhesus HDN is usually caused by immune anti-D and less commonly by other Rhesus antibodies. It occurs when a Rh negative mother with circulating IgG anti-D antibody (formed from a previous Rhesus
incompatible pregnancy) becomes pregnant with a Rh positive infant and IgG anti-D passes into the fetal circulation, destroying fetal cells. The infant can
be born severely anaemic and jaundiced.

The severity of disease increases with each Rh positive pregnancy. Infants with Rhesus HDN are usually more severely affected than infants with ABO HDN.
Note: In most cases of Rhesus HDN, maternal IgG anti-D will have been detected by the laboratory during routine antenatal visits, and the strength of the antibody (titre), monitored.
When Rhesus testing is not performed routinely (due to low frequency of Rh negative persons in the population) and an infant is born severely anaemic
and jaundiced, the laboratory may be asked to investigate the possibility of Rhesus HDN.

See also:laboratory investigation of HDN

HOW TO COLLECT CAPILLARY BLOOD

Capillary blood can be collected from:


The ‘ring’ finger of a child or adult
Do not stick the thumb or index finger
as these are the most sensitive.

The heel of an infant up to one year old Care must be taken not to damage the heel by sticking it too near the edge or by holding it too forcibly

Make sure the puncture area is warm to allow the blood to flow freely. On cold days soak the hand or foot of an infant in warm water prior to collecting a sample.


1 Cleanse the puncture area with 70% ethanol. Allow the area to dry.

2 Using a sterile pricker or lancet, make a rapid puncture, sufficiently deep to allow the free flow of blood

3 Wipe away the first drop of blood with a dry piece of cotton wool and use the next few drops for the test. Do not squeeze too hard because this will result in an unreliable test result.

4 When sufficient blood has been collected, press a piece of dry cotton wool over the puncture area until bleeding stops.