Use of filter paper for the collection and analysis of human whole blood specimens.

The Centers for Disease Control and Prevention and its partners have been operating the Newborn Screening Quality Assurance Program for >20 y. The program helps participating laboratories to evaluate and improve the quality of their newborn-screening testing efforts by providing quality control dried blood spot materials and proficiency-testing materials for the external evaluation of screening programs. The Newborn Screening Quality Assurance Program provides an independent evaluation of filter papers approved by the Food and Drug Administration for the collection of blood for clinical tests. These activities have created a mechanism for the validation of the filter paper blood collection device and the standardization of materials and methods for the analysis of dried blood spots.

Oral zidovudine during labor to prevent perinatal HIV transmission, Bangkok: tolerance and zidovudine concentration in cord blood. Bangkok Collaborative Perinatal HIV Transmission Study Group.

OBJECTIVES: To evaluate tolerance for the oral administration of zidovudine (ZDV) during labor and measure the resulting ZDV concentrations in umbilical cord blood. DESIGN: A cross-sectional study of women in a placebo-controlled trial of short-course ZDV (twice a day from 36 weeks' gestation until labor and every 3 h during labor) to prevent perinatal HIV transmission in Bangkok. METHODS: Umbilical cord blood was collected. Sixty control specimens and specimens from 372 women (182 in the ZDV group, 190 in the placebo group) were tested for ZDV by radioimmunoassay (lower detection limit < 1 ng/ml). RESULTS: All women in the ZDV group took one or more labor dose, 170 (93%) took their last dose within 3 h of delivery, and only five (3%) experienced nausea or vomiting, a proportion similar to the placebo group. The median concentration of ZDV in the cord blood in the ZDV group was 252 ng/ml (range, < 1-1133 ng/ml); 31 (17%) specimens were less than 130 ng/ml (0.5 microM), the concentration thought to be active against HIV in vitro. Median concentrations were 189 ng/ml in specimens from women taking one or two labor doses, 290 ng/ml in those taking three or four doses, and 293 ng/ml in those taking more than four doses (P < 0.01). The ZDV concentration was not associated with time since the last dose, body weight, or perinatal transmission. CONCLUSION: Oral intrapartum ZDV was feasible and well tolerated. Most ZDV concentrations in the cord blood after oral dosing during labor were at therapeutic concentrations but were lower than those reported after continuous intravenous administration. Although concentrations were not associated with perinatal transmission, these data do not exclude the possibility that intrapartum and neonatal chemoprophylaxis is effective.

Radioimmunoassay for monitoring zidovudine in dried blood spot specimens.

We modified and evaluated a RIA for serum and used the modified RIA to measure zidovudine in dried blood spot specimens (DBSs) routinely collected for newborn screening and tested anonymously for maternally acquired HIV antibodies in the national HIV Seroprevalence Survey Among Childbearing Women. DBS calibration and quality-control materials were used to adapt the serum assay to the DBS matrix. The assay had a limit of detection of 24 micrograms/L serum and was used to measure zidovudine from both whole DBSs and the eluate remaining after HIV antibody screening. We initiated a pilot study to investigate the assay's performance and assess its potential to determine the implementation of the US Public Health Service recommendations that HIV-infected pregnant women and newborns receive zidovudine treatment to reduce the risk of perinatal HIV transmission.

Method-dependent variations in the stability of apolipoprotein B in a stabilized liquid reference material.

Using accelerated Arrhenius-type short-term and long-term temporal studies, we evaluated the storage life of a stabilized, liquid-frozen reference material (SLRM) for human apolipoprotein B (apo B) developed by the International Federation of Clinical Chemistry. As measured by our candidate reference RIA, the concentrations of immunoreactive apo B in the SLRM showed pronounced degradation with exposure to increasing temperatures over time. The SLRM was stable for as long as 1 year when stored at - 70 degrees C, but its immunoreactive apo B declined by < 10% when stored at 4 degrees C for 10 months. Using radial immunodiffusion and an ELISA to assess the equivalency of measured mass for the accelerated thermal stability of the SLRM, we found a loss of immunoreactive apo B similar to that measured by RIA. Analyzing the same samples by liquid immunoprecipitation (nephelometry) resulted in the amount of apo B present being overestimated, especially in samples held for long periods. By using different immunological methods to evaluate this thermally aged SLRM, we demonstrated that its measured behavior varies depending on the method of quantitation.

International Federation of Clinical Chemistry standardization project for measurements of apolipoproteins A-I and B. IV. Comparability of apolipoprotein B values by use of International Reference Material.

We performed temporal and thermal stability studies on SP3-07, a liquid-stabilized reference material for apolipoprotein (apo) B, selected during the previous phase of the International Federation of Clinical Chemistry project on standardization of apolipoprotein measurements. Results indicate that SP3-07 stored at -70 degrees C has the long-term stability required for a reference material. We assigned an accuracy-based apo B value of 1.22 g/L to SP3-07, using a nephelometric method that was calibrated with freshly isolated low-density lipoprotein for which the apo B mass value was determined by a standardized sodium dodecyl sulfate-Lowry procedure. Using a common protocol, the study participants transferred the assigned mass value from SP3-07 to the individual calibrators of the analytical systems and measured the apo B concentration of 20 fresh-frozen samples obtained from individual donors and covering a clinically relevant range of apo B values. The among-laboratory CV on these samples, analyzed by 25 analytical systems, ranged from 3.1% to 6.7%. These results demonstrate the lack of matrix effects of SP3-07 and its ability to provide accurate and comparable apo B values in a variety of immunochemical methods. On the basis of the outcome of these studies, the World Health Organization has endorsed SP3-07 as the International Reference Material for Apolipoprotein B.