Prenatal diagnosis of the Rhesus D fetal blood type on amniotic fluid in daily practice

OBJECTIVE

To retrospectively examine the diagnostic accuracy of prenatal RhD blood type genotyping on amniotic fluid, using a combination of two polymerase chain reaction (PCR) methods in daily practice.

METHODS

Amniotic fluid was obtained from women undergoing amniocentesis. Two PCR protocols were carried out in two different laboratories. We obtained the postnatal serological RhD status. In cases with differing prenatal and postnatal test results, we investigated the possible error source by different methods. Sensitivity, specificity and the predictive values were calculated.

RESULTS

Prenatal RhD genotyping was applied in 1,640 cases, of which the postnatal serologic RhD status was obtained in 927. No discordance between both PCR methods occurred. In nine out of 927 cases differing results between PCR and serologic status were encountered. The sensitivity was 99.5%, the specificity 98.6%, and both positive and negative predictive values 99.1%.

CONCLUSION

Prenatal diagnosis of the fetal RhD blood type with PCR from amniotic fluid is highly accurate in daily practice and associated with a minimal sensitivity of 99.5% and a minimal specificity of 98.6%.

Gastrointestinal absorption of metals (51Cr, 65Zn, 95mTc, 109Cd, 113Sn, 147Pm, and 238Pu) by rats and swine

Adult and neonatal rats and neonatal pigs were gavaged with solutions of metal radionuclides to determine gastrointestinal absorption. Zinc-65 and technetium-95m were well-absorbed by both age groups; chromium-51, cadmium-109, tin-113, promethium-147, and plutonium-238 were not. The quantities of the poorly absorbed metals that were absorbed by neonates were between 4 and 100 times higher than those absorbed by adult rats. Autoradiograms prepared from the entire small intestine of the neonatal rat showed that 109Cd was retained in the duodenum. In contrast, measurements in the piglets showed much higher 109Cd retention in the ileum than in the duodenum. Autoradiograms and radiochemical measurements of 147Pm and 238Pu in both neonatal rats and swine showed the highest level of retention in the ileum. The results indicate that, for most of the metals studied, absorption from the gastrointestinal tract is substantially higher for neonatal than for adult rats.

Volume Change Accompanying Rubber Extension

A new equation for the volume dilation accompanying rubber extension is obtained from a reinterpretation of the kinetic theory equation for rubber elasticity. This equation is shown to describe published volume-extension data better than either that derived from simple kinetic theory or that derived from the Mooney-Rivlin equation.