Familial discrepancy between the one-stage and two-stage factor VIII methods in a subgroup of patients with haemophilia A.

A higher result for plasma factor VIII:C measured by the one-stage as compared with the two-stage method has been described in some patients with haemophilia A or with von Willebrand's disorder. We used both methods to measure FVIII:C in 95 patients with haemophilia A. The results were equivalent in all 21 patients with severe haemophilia (16 families) and in 45 of the patients with mild or moderate haemophilia (18 families). However, the results were discrepant (FVIII:C by one-stage assay 2-7-fold higher than by two-stage assay) in the other 29 patients with mild or moderate haemophilia (12 other families). For each patient with discrepant FVIII:C results the classification was the same for all other affected members of his family. In some families with haemophilia A the gene defect leads to a discrepancy between the one-stage and two-stage FVIII:C results and may be more widespread than previously recognized.

Effect of concentration of trisodium citrate anticoagulant on calculation of the International Normalised Ratio and the International Sensitivity Index of thromboplastin.

The aim of this study was to determine whether the concentration of trisodium citrate used to anticoagulate blood has an effect on the INR of the sample and the ISI of the thromboplastin. Five thromboplastins including and Australian reference material were used to measure the prothrombin time of normal and patient samples collected into two concentrations of trisodium citrate--109 mM and 129 mM. There was no effect of citrate concentration on the INRs determined with the reference material. However for the other four thromboplastins there was a significant difference between INRs for the two citrate groups. The prothrombin times of the samples collected into 129 mM were longer than those collected into 109 mM. This difference was only slight in normal plasma but more marked in patients receiving oral anticoagulants, causing the INRs for patient plasmas collected into 129 mM citrate to be higher then the corresponding samples collected into 109 mM citrate. From orthogonal regression of log prothrombin times by the reference method against each thromboplastin, we found that the ISI for each thromboplastin was approximately 10% lower when determined with samples collected into 129 mM citrate than with samples collected into 109 mM. These results suggest that the concentration of trisodium citrate used for collection of blood samples can affect the calculation of the INR and the calibration of the ISI of thromboplastin. This was found both for commercial thromboplastins prepared by tissue extraction and for a recombinant tissue factor.

Prostatic surgery for benign prostatic hyperplasia: meeting the expanding demand.

We describe changes in the pattern of surgery for benign prostatic hyperplasia (BPH) in Scotland between 1971 and 1989. The data are based on an analysis of routinely collected Scottish hospital in-patient statistics for primary prostatic operations on men with a diagnosis of BPH (ICD Code 600.0). Primary operation age-adjusted rates for BPH increased from 8.9 to 15.8 per 10,000 male population from 1971 to 1989. This was accompanied by a reduction in bed day use for BPH surgery from 49,500 bed days in 1971 to 36,000 in 1989. Case fatality for all surgery for BPH also fell steadily and can no longer be regarded as a relevant measure of prostatectomy outcome. Virtually all surgical intervention is now transurethral resection (TUR), forming 94% of surgery for BPH in 1989 compared with only 32% in 1971. The increase in surgical procedures carried out for BPH has been greater in younger age groups. If the pattern of increasing surgical intervention in the management of BPH over the past few years continues and there is an increased demand for treatment, and if the reported demographic changes occur, there will be a need for an additional 9 new consultant urologists in Scotland by 2001. Even if present operation rates hold steady, population changes alone will produce enough work for 2 more urologists.

Detection of haemophilia carriers: multivariate analysis compared with discriminant analysis using up to five factor VIII variates.

Multivariate analysis is potentially superior to the linear discriminant analysis which is commonly used to identify carriers of haemophilia. Our aim was to compare these two statistical methods, and to find which factor VIII variates most effectively partitioned carrier and normal subjects. In this study we assayed one- and two-stage factor VIII coagulant activity, factor VIII related antigen by electroimmunoassay and by fluoroimmunoassay, and ristocetin co-factor in 50 normal females and 50 carriers of haemophilia. From the results we calculated multivariate ellipses which circumscribed the normal and the carrier populations, and we displayed these on the monitor of a microcomputer. These ellipses separated the two populations better than linear discriminants calculated on the same data. Multivariate analysis correctly identified 94% of the carriers whereas discriminant analysis correctly identified only 84%. Discriminant analysis gave poorer results because the statistical assumption of equal variance was breached, whereas the assumption of multivariate normality was upheld. Of the five factor VIII variates, two-stage factor VIII coagulant activity and factor VIII related antigen by electroimmunoassay correctly identified the most subjects. Ristocetin co-factor did not improve the diagnostic ability, either when in lieu of or when added to factor VIII related antigen.

The effects of age, gene source and familial severity on Factor VIII in normals and haemophilia carriers: analysis by multiple regression.

There are conflicting views on the effects of age, gene source and familial severity on levels of factor VIII in carriers of haemophilia. Different workers have found that factor VIII increases with age, is higher in paternal carriers, and is higher in carriers from families with more severe haemophilia. Other workers have disagreed with these findings. In this study we explored some of the causes of this conflict. We measured factor VIII related antigen and factor VIII coagulant activity on 40 normal females and 48 carriers, and analysed the results by multiple regression and analysis of covariance. Our results indicated that both factor VIII coagulant activity and factor VIII related antigen increased with age, but were unaffected by the familial severity of haemophilia or whether the defective gene came from the mother or the father. We found that the conflicting reports of previous authors were due to high inter-correlations of the studied variables.

Comparison of standardization techniques for colorimetric analyses on a centrifugal analyzer.

The influences of the mode of standardization and the type of standard on the precision of four mechanized methods performed on a centrifugal analyzer are described. Experimental results show that the mode of standardization -- variable, using a standard in each analytical batch, and constant, using a direct relationship between concentration and absorbance -- must be objectively selected. If the variable mode is chosen, the type and level of standard must be carefully chosen and absorbance of assays of the standard must be carefully monitored for good quality control. It is recommended that the optimum standardization technique and standard, where applicable, should be assessed and subsequently documented in evaluations of methods, kits and instruments.

The stability of coagulation factors in stored blood.

The complete coagulation profile of citrate phosphate dextrose (CPD) stored blood has been studied during 21 days storage at 4 degrees C. Ten donations were studied at zero, one, seven, 14 and 21 days. One donation contained small clots and was studied separately. Activities of factors I, II, IX, XII or XIII did not deteriorate significantly. Slight, but clinically unimportant deterioration occurred in factors VII, X and XI. There was marked deterioration in activities of factor V, and factor VIII, the levels decreasing from 1.0u/ml at day zero to 0.51 to 0.30 respectively at day 21. The donation which contained small clots had more marked decreases in factors V and VIII from the first day. The general stability of coagulation factors suggests that even massive blood replacement is unlikely to result in clinically significant coagulation defects.

Metabolic and cardiovascular side effects of the beta 2-adrenoceptor agonists salbutamol and rimiterol.

The metabolic and cardiovascular side-effects of intravenous infusions of therapeutic doses of beta 2-adrenoceptor agonists salbutamol and rimiterol have been determined in four healthy male subjects. There were dose-related increases in plasma glucose, renin activity, serum insulin and heart rate, and significant hyperlactataemia and ketonaemia. There were dose-related decreases in plasma potassium, phosphate and corticosteroids and significant hypocalcaemia and hypomagnesaemia. The effects of equivalent molar amounts of salbutamol and rimiterol were similar. Whichever drug is used, special care is required with patients who may have abnormal glucose tolerance, potassium depletion, or be predisposed to lactic acidosis. Rimiterol may be preferable for infusion because of its short plasma half-life.

Comparison of standardization techniques for manual colorimetric analyses.

The influence of both the mode of standardization and the type of standard on the precision of four manual colorimetric methods performed under optimal conditions variance is described. The terms variable calibration mode and constant calibration mode are proposed; these describe standardization by within-run standards and standardization by a predetermined calibration relationship between concentration and absorbance that remains constant over a fixed period of time. We show that calibration relationships and mode of standardization must be established for each and every individual method on objective evidence. Where within-run standards are used, they must be carefully selected for each method. The implications for method evaluation and quality control are discussed.

An inhibitor of fibrin formation in thromboplastins prepared by saline extraction of human brain.

Human brain is a common source of thromboplastin for the prothrombin time, where the end point is the conversion of fibrinogen to fibrin. Experiments showed that human brain also contains a proteolipid which inhibits the conversion of fibrinogen to fibrin. The proteolipid is removed when brain tissue is washed with acetone, but remains as a contaminant when brain is extracted with saline. For this reason prothrombin times on the same plasma are longer when saline extracts, rather than acetone dried preparations, are the source of thromboplastin. The proteolipid explains why the prothrombin time becomes shorter when saline extracts are diluted to standardize their activity against the British comparative thromboplastin.

Pictorial reporting of multiple thyroid function results.

Clinicians experience difficulty in correctly interpreting the results of in vitro thyroid function tests in the presence of abnormalities of thyrobinding proteins or when results are borderline. This difficulty has been largely resolved in our laboratory by three innovations. First, the borderline areas for each of three routine tests of thyroid function (total thyroxine, thyrobinding index, and free thyroxine index) were accurately determined. Second, the results from this routine profile of three tests were displayed pictorially so as to produce patterns characteristic of various diagnostic situations, including euthyroidism in the presence of abnormalities of thyrobinding proteins. Third, interpretive comments and, in the case of borderline patterns, suggested further testing procedures were added to the report. Clinicians find the reporting system helpful and respond when additional tests are suggested. The system, operated manually at first, was later computerized.

Current "corrected" calcium concept challenged.

There is wide individual variation in the number of millimoles of calcium bound per gram of albumin in the serum. Individual regression coefficients for serum calcium concentration on serum albumin concentration have been determined in 62 people (25 of our own patients and 37 reported by others). The 95 percentile range was 0-007-0-053 mmol/g, with a median value of 0-025 mmol/g. Accordingly, it is not valid to "correct" a person's measured serum total calcium concentration for variations in serum albumin concentration using an average regression coefficient. Rather, the individual's own regression coefficient must be used. A tourniquet test seems to be the simplest technique for determining this value. Even then, precise interpretation of an individual's corrected serum calcium concentration is possible only when an appropriate reference range for corrected serum calcium concentration has been established. Such an appropriate reference range must be determined from an adequate number of normal people using the individual's own correction factor in each case.