A sample of clotted blood is taken for all women attending antenatal clinic and the tests performed include
- ABO and Rh. By the usual standard tube method
- Antibody screening can be done by using pooled group O rbcs. Cells should to treated with enzyme (papain). Then use this to treat patients serum at 37C. Enzyme treatment of rbc is necessary for detection of Rh abs and other abs belonging to the kell.
- Specificity:- Having determined that it has immune abs., determine the specificity the a panel of cells which include R R, R1, R2, R2 R2, R, rI rII, rr samples.
- Then titrate to determine the strength antibody’s present treat factors effecting the results (1) such as ab. Uptake which depends out only on the ab. Ppta. But also on the building of constant of the ab. Diff in vivo-vitro. (2) Variation in avidity and distinctive of high distinctive power (3) ability of the in fat to cope with the disease (4) Rh. Genotype of the child R2r CDe because titro of D in Cde is less C masks it. (5) Rl genotyping of the father. This is necessary because if the faltering reenogygeus for D R1,R2, R R, R2 R2 it means that all the children will be effected but if he is heterozygen R2r R2r then some for
Most reliable test to be done to tell the clinician reliability the poss. It proves of which amniotic fluid with typed from the foctel cavity and its bile pigment we esund spectro metrically of is now know that the out of bailment present is related to the severity of the HDN when the optical density of the amniotic fluids estimated at diff. wavelength over the range 400-600nm, of the shape seen belows is obtained.
Fluid from a pregnant mother with a severely affected infact shows a greatly increased O.D with a peak between 450 and 460 nm. Normal pregnancy shows with between 450-460 of about 0.05 at 30weeks falling to 0.02 at full term slight or no increase in absorbance-infant is not risk; moderate increases-infant is at low risk marked increase-infant is seriously affected and at risk of intra uterine death.
In serum bilirubin, serum or plasma is treated with diazotized sulphonili acidic with the addition of methanol to accelerate the reaction of unconjugeted bilirubin. The red colour produced is compared in a photo electric colorimeter with that of a freshly prepared bilirubin std. or with an artificial standard.
Conjugated bilirubin alone is measured by carrying out the reaction without methand. In normal infants serum bilirubin is the range of 3mg/100 while affected infants record 10mg/100
Investigation of HDN due to ABO incompatibility
Ratio is 1 in 150
And I in 3000 will be so severe that exchange transfusion becomes necessary
Actiology – usually a group O mother given birth to A or B foetus.
Mechanism of Action:- Disease is caused by lgG anti A or anti B which is capable of crossing the placenta. Infant develops jaundice within the 1st -24hours of life and this might necessitate exchange transfusion.
Serology:- Difficult to diagnose. The direct coombs which is always positive in Rh. Disease is always-this case negative.
Proff: The only proof of HND due to ABO in compatibility in the demonstration of either incomplete anti A or a for a group A body cells or anti B in the eluate from a group B
Other findings can only indicate perhaps ABO in compactions is cause of the AND.
Hazards of amniocentesis
- The most serious hazard from amniocentesis seems to be the puncture of factel blood vessels.
- The introduction of a needle into the amniotic cavity evidently causes further potential hazards eg introduction of bacteria.
- Risk of immungection another risk from amniocentesis is that foetal with will be punctured and foetal rbcs will then enter the mothers incitation. The magnitude of this risk is difficult to assess.
Investigation of HDN
(a) Hb ? 13.6 mean 16.6gm%
(b) PCV 52%
(c) Blood film microspehnocytes erythroblasts
- D.C.T. always positive in Rh incompatibility
- ABO Rh –std tube technique
- serum bilirubin > 10mg/100ml
In the Rh. Grouping, saline anti D must be used and AB serum as negative control Albunien reacting anti D will block binding sites and give a false negative result if the cells are strongly sensitized.
is used with incomplete anti D it gives a results because albumin will cause legel cells to agglituiete owing to this being std = maternal ab. And due to those being a reaction between the serum and of antigen
- Std tube technique
- DCT-always negative
- Elution: This is because incomplete anti A or anti B can often be eluated from cells by lawsteners heat method. The eluate is tested against adult std A and B cells by ICT. The cells could be enzyme treated or the albunin addition technique used at 37C
- Free antibody: Cord serum after the mother. The seme is therefore tested against lgG anti A or lgG anti B as for the eluate.