Midtrimester screening for microalbuminuria in healthy pregnant women.

To ascertain the effectiveness and feasibility of testing for microalbuminuria and the albumin/creatinine ratio as an early indication of hypertensive disorders of pregnancy, we measured albumin and creatinine excretion in 95 healthy pregnant women between 16 and 20 weeks of pregnancy. Nine women developed hypertensive complications; one of them became pre-eclamptic. There were no statistically significant differences in urine albumin and creatinine concentrations nor in the albumin/creatinine ratio between those women who developed pregnancy-induced hypertension and those who did not. Microalbuminuria testing had a specificity of 0.95 (95% CI: 0.88 - 0.99) and a sensitivity of 0.11 (95% CI: 0.03 - 0.48). The albumin/creatinine ratio had a specificity of 0.98 (95% CI: 0.92 - 1.0) and a sensitivity of 0.22 (95% CI: 0.03 - 0.6). The albumin/creatinine ratio was significantly lower in women who delivered prematurely. We conclude that mid-trimester testing for microalbuminuria and the measurement of the urinary albumin/creatinine ratio are not effective tools for the early recognition of pregnancy-induced hypertension in healthy pregnant women.

Vitamin K1 levels and coagulation factors in healthy term newborns till 4 weeks after birth.

Vitamin K1 serum levels were assessed by means of an off-line multidimensional liquid chromatography in 18 mothers, shortly after delivery, and in their healthy term infants. Umbilical cord and venous blood samples were assayed up to 4 weeks of life. Concurrently, levels of coagulation factors II and X, antithrombin III and platelets were established. Although the detection limit of the assay was as low as 22 pg/ml, vitamin K1 concentration appeared to be still beyond that level in cord blood or in newborn serum within 30 min after birth, whereas vitamin-K-dependent coagulation factors are already at a level of 40%, without evidence for the presence of descarboxy prothrombin, in any of the investigated neonates. After 3 days, breast-fed neonates had lower vitamin K1 levels than formula-fed infants (0.76 and 1.44 ng/ml, respectively). The levels of the vitamin-K-dependent coagulation factors II and X, however, were comparable, regardless of the kind of feeding. After 28 days, breast-fed neonates had even lower vitamin K1 levels (0.49 ng/ml, while the formula-fed infants showed higher vitamin K1 levels (4.45 ng/ml). But even then, the levels of vitamin-K-dependent coagulation factors II and X were comparable, regardless of the kind of feeding. From this we conclude that the serum levels of vitamin K1 in formula-fed neonates exceed those of breast-fed infants from the moment of feeding (24 h and later) without a concomitant rise in vitamin-K-dependent coagulation factors. A relationship between vitamin K1 levels and vitamin-K-dependent coagulation factors could not be established in healthy term breast-fed or formula-fed infants.

A comparison of the screening ability of two automated leukocyte differential counters.

The ability to screen out abnormal leukocyte differential counts by the H 6000TM and the Hematrak 590TM has been evaluated, using the visual 100 cell differential as a reference. Optimization of the discrimination levels for both instruments by the use of linear regression procedures and "Receiver Operating Characteristics (ROC) curves" and its impact on their performance characteristics is discussed. The overall sensitivity for 314 outpatient/188 inpatient samples was 0.84/0.94 for the H 6000 and 0.84/0.88 for the Hematrak, respectively. The overall specificities for out-/inpatient samples were found to be 0.61/0.44 and 0.47/0.30 for the H 6000 and the Hematrak, respectively. Both instruments had very similar screening abilities for the detection of abnormal leukocyte differential counts. However, the H 6000 flags correlated better with the visual findings than the Hematrak flags as demonstrated by the parameter-sensitivity and predictive value calculations and by the ROC curves.

Determination of low molecular weight heparin in clinical laboratory.

The applicability was investigated of automated spectrophotometric heparin assays and three clotting assays for determination of two low molecular weight (LMW) heparin fractions: Org 10172 and DxN10 and two infractionated commercially available heparins. The relative activity of the two commercially available heparins was similar in the anti-Xa assay, in the anti-IIa assay and in 3 clotting assays. The LMW heparins showed markedly different relative activity in all 5 assays. The activities of those heparin preparations relative to the standard heparin were compared in the 5 assays, but standardization against a standard heparin preparation appeared impossible. Methods of heparin determination can be used to monitor treatment with a heparin preparation only if the same preparation is used as a reference substance.

Heparin neutralization during collection and processing of blood inhibited by pyridoxal 5'-phosphate.

Spectrophotometric heparin assays are expected to be independent on clotting factors, either activated or nonactivated, but could be sensitive to heparin neutralization during blood collection. It was shown that more than 200 U of heparin/l plasma can completely be neutralized during blood processing. Because the heparin neutralization is not constant but dependent on the sample as well as on the type of sample handling, one cannot beforehand compensate and correct the results for possible heparin neutralization. We tested the use of pyridoxal 5'-phosphate (PLP) to prevent heparin neutralization. As the use of PLP in the citrate tube decreased the heparin neutralization to a negligible effect, PLP-citrate tubes are to be preferred for all plasma heparin determinations.

Automated determination of heparin with chromogenic substrates.

Spectrophotometric heparin assays which are based on the catalytic effect of heparin on either the inactivation of thrombin or that of factor Xa by antithrombin III, were adapted for use in a laboratory batch analyzer. Optimal conditions were determined for assays using the chromogenic substrates Chromozym-Th and S-2238 with thrombin, and S-2222 with factor Xa. Inactivation of the clotting enzyme by antithrombin III was stopped by addition of chromogenic substrate. Assays thus obtained appeared to be applicable in a wider range of heparin concentrations and were less dependent on plasma antithrombin III concentration that known manual spectrophotometric methods. The best results were obtained with the methods based on thrombin inactivation and applying a logarithmic reference curve.

Automated spectrophotometric heparin assays. Comparison of methods.

Three automated spectrophotometric heparin assays were investigated. The day-to-day reproducibilities in routine laboratory use were compared with two commercial manual kits for heparin determination. Regression analysis of the activated partial thromboplastin time (APTT) on results of any of the heparin assays shows that the heparin concentration cannot be deduced from the APTT values found in patients receiving heparin. The automated heparin assays that employ thrombin and Chromozym-Th or S-2238 were found to be most suitable for routine heparin determination. Heparin concentrations obtained from assays based on factor Xa inactivation were not significantly different from those employing thrombin (p less than 0.01), but revealed a wider standard deviation. The relationship between APTT and heparin level found was not related to the plasma antithrombin III concentration. The extra antithrombin III that is added in the assays had to be freed of heparin neutralising activity to obtain reliable estimates of the heparin concentration in the low range (0-200 U/l).

An evaluation of immunoglobulin assays on the ACA III.

We evaluated an immunoturbidimetric Du Pont ACA method for the determination of IgG, IgA and IgM in serum. Between-day reproducibilities of the ACA assays were comparable to those of a radial immunodiffusion, a Hyland nephelometric and a turbidimetric assay on Centrifichem 400. Correlations between results obtained by these methods were acceptable, but the results differed quantitatively. After simulated recalibration based on results of control sera or patient samples, the results for IgA and IgM became more interchangeable. IgM concentrations below 0.25 g/l, which are important for the assessment of intra-uterine infections, could not be quantified with the ACA. Moderate levels of haemoglobin, bilirubin or lipids do not interfere with the ACA assays. The evaluated assays are fast and easy to use.

Interindividual variation in relationships between plasma heparin concentration and the results of five heparin assays.

In order to determine their value for estimating the heparin concentration in plasma, we established the relationship between test result and heparin concentration in plasma from various individuals, for five assays used with heparin treatment. Only assays which can be carried out routinely in clinical laboratories were considered. The thrombin time and the whole blood recalcification time give pointless and ambiguous information respectively, concerning the heparin level. The activated partial thromboplastin time with and without heparin neutralisation give only a rough estimate. The spectrophotometric method using a chromogenic substrate gives the best information. The latter can be improved by using a non-linear (parabolic) equation for the calculation of the reference curve. Current heparin therapy, controlled with the aid of a clotting assay, may result in plasma heparin concentrations that vary widely from one patient to another.

Two serum pancreatic isoamylase determinations compared.

Serum pancreatic isoamylase activity was measured by a method involving inhibition of salivary isoamylase and by a well-known agarose electrophoretic method, modified by us. We saw changes in electrophoretic patterns of pancreatic isoamylase fractions after storage of serum samples for three weeks at 4-8 degrees C, but with the inhibition method no alterations in activities were found. Within-assay and between-assay imprecisions of both methods were about the same. Serum pancreatic amylase activities as measured by the inhibition method exceeded by about 10% those obtained by the electrophoretic method. The inhibition method seems to be a reasonable candidate for routine application, whereas the electrophoretic method is still time-consuming and requires special skill to perform. Some suggestions are given for improving the calibration of the inhibition method recommended by the manufacturer.