The Human Tissue Act: implications for clinical biochemistry.

The Human Tissue Act sets out a new legal framework for the use and retention of tissues from living persons as well as the removal, retention and use of tissue and organs from the deceased. The Human Tissue Authority (HTA) has been established as the regulatory body in relation to the Act and also to give advice and guidance initially through the publication of Codes of Practice. The HTA will also license activities within the remit of the Act and will inspect to ensure compliance with the Act and licence conditions. The Act establishes consent as the essential requirement for the lawful retention and use of tissues and organs; failure to comply could result in penalties that include a custodial sentence. In addition to solid organs and tissues, the Act applies to the use of other specimens including body fluids if they contain cells. Tissue can be stored and used without consent for a number of purposes on the basis that these are integral to the general provision of clinical and diagnostic services. These include clinical audit, education or training relating to human health, performance assessment and quality assurance. In the case of research, the Act allows tissue to be used without consent, provided that the tissue is anonymized so that the researcher cannot identify from whom the material came. Linking with medical records is allowed, provided patient-identifying information is not obtained. There is a requirement to respect the wishes of any patient who specifies that they do not wish diagnostic or therapeutic samples to be kept or used for additional purposes.

Lowering of plasma glucose concentrations with bezafibrate in patients with moderately controlled NIDDM.

The goal of this study was to investigate whether treatment with bezafibrate improves glucose tolerance in non-insulin-dependent diabetes mellitus (NIDDM). The study included 37 NIDDM patients with HbA1 concentrations greater than 8.5% and normal kidney and liver function who were being treated with diet alone or diet together with a sulfonylurea drug. One patient withdrew because of constipation. At randomization and after 3 mo of treatment, patients were given a standard mixed-test-meal tolerance test (MTT; 500 cal) after an overnight fast, and plasma glucose, insulin, C-peptide, metabolite, nonesterified fatty acid (NEFA), and triglyceride concentrations were measured at 15- to 30-min intervals. Serum lipid, HbA1, and fructosamine concentrations were measured at monthly intervals. Glucose, NEFA, and triglyceride concentrations were significantly lower throughout the second MTT in bezafibrate patients (P less than 0.01-0.001) but not in the placebo group. Fasting serum insulin and C-peptide levels, but not postprandial concentrations, were reduced only in bezafibrate patients (P less than 0.05). After 3 mo, mean fasting serum triglyceride concentrations fell from 2.2 to 1.4 mM (P less than 0.001), total serum cholesterol concentrations from 6.3 to 5.5 mM (P less than 0.001), and low-density lipoprotein cholesterol concentrations from 4.2 to 3.5 mM (P less than 0.001) in bezafibrate patients. There were no changes in serum lipid concentrations in the placebo group. Treatment of patients with moderately controlled NIDDM with bezafibrate improves glucose tolerance and the serum lipid profile. Bezafibrate treatment may be a useful adjunct to hypoglycemic therapy in patients with NIDDM.

Lack of effects of hypoglycemia on glucose absorption in healthy men.

OBJECTIVE: To assess the effects of hypoglycemia on glucose absorption by examining the systemic appearance of 3-OMG (a glucose analogue that is transported by the same mechanism as glucose) after oral administration. RESEARCH DESIGN AND METHODS: Six healthy males 22-31 yr of age were studied during a hypoglycemic (50 mg [2.7 mM]/100 ml) and a euglycemic (90 mg [5.0 mM]/100 ml) glucose clamp. At 50 min after exposure to insulin, an oral glucose load containing 20 g of glucose and 4.5 g of 3-OMG dissolved in 300 ml of tap water was administered. Insulin administration was interrupted 30 min after oral glucose administration. RESULTS: Plasma glucose was clamped at 88 +/- 1.3 mg (4.9 +/- 0.1 mM)/100 ml during euglycemia and at 50 +/- 1.9 mg (2.7 +/- 0.1 mM)/100 ml during hypoglycemia. Concentrations of glucagon, growth hormone, cortisol, and epinephrine were significantly elevated during hypoglycemia. After 60 min, circulating 3-OMG concentrations increased to zeniths of 11.4 +/- 0.2 mg (585 +/- 10.0 mM)/100 ml (hypoglycemia) and 11.6 +/- 1.1 mg (585 +/- 56.0 microM)/100 ml (euglycemia; P = 0.95). Absorption of 3-OMG was evident between 15 and 20 min after administrations in both situations. Serum insulin was significantly lower during hypoglycemia compared with the control situation (345 +/- 50 microM [hypoglycemia], 445 +/- 50 microM [euglycemia], P = 0.03). CONCLUSIONS: We conclude that hypoglycemia does not seem to affect intestinal absorption of glucose as judged by systemic appearance of 3-OMG.

Lipogenesis in isolated human sebaceous glands.

Lipogenesis in isolated human sebaceous glands from [U-14C]glucose, [U-14C]leucine, [U-14C]isoleucine, and [U-14C]valine has been determined by thin-layer chromatography. Total lipogenesis from 2 mmol/l [U-14C]glucose was 114.8 +/- 22.3 pmol/gland per h (mean +/- SE), with 53.8% being incorporated into triglycerides, 20.2% into squalene, 12.8% into phospholipids, 2.1% into cholesterol and 7.1% into wax monoester and cholesterol ester and 5% into di- and monoglycerides and free fatty acids. Total lipogenesis from 2 mmol/l [U-14C]leucine, 2 mmol/l [U-14C]isoleucine, and 2 mmol/l [U-14C]valine in the presence of 2 mmol/l glucose was 26, 29 and 9%, respectively, of that seen with 2 mmol/l glucose alone. The pattern of 14C distribution in the various lipid classes from the three U-14C-labelled branched-chain amino acids was not significantly different from that seen with [U-14C]glucose.

Lipid lowering therapy leads to a reduction in sodium-lithium countertransport activity.

Erythrocyte sodium-lithium countertransport (SLC) was measured in 17 patients with either combined hyperlipidaemia or hypercholesterolaemia before and after lipid lowering therapy. Before treatment SLC related to the serum triglyceride level and was increased in combined hyperlipidaemia. After treatment the SLC had returned to normal and the change in SLC was related to the change in serum triglyceride levels. Raised SLC is associated with essential hypertension but is not related to blood pressure. Therefore, the association of raised SLC with hyperlipidaemia and essential hypertension appears to have different underlying mechanisms.

Microalbuminuria and associated cardiovascular risk factors in the community.

The prevalence of microalbuminuria and relationship to cardiovascular risk factors was examined in a cross-sectional community survey of cardiovascular risk factors. Microalbuminuria (when classified as albumin concentration greater than 20 micrograms/ml) was present in 6.3% of subjects but in conjunction with an albumin/creatinine ratio greater than 3.5 in only 2.2%. Diastolic blood pressure, prevalence of abnormal electrocardiographs, and to a lesser extent systolic blood pressure and fibrinogen concentration, were greater in those with albuminuria concentrations greater than 20 micrograms/ml. The strongest positive univariate correlates of albumin/creatinine ratios in those with detectable albuminuria were age, fibrinogen, blood pressure, total- and low density lipoprotein-(LDL) cholesterol, apo B and alcohol intake, whereas fasting insulin and insulin resistance were inversely correlated. Multiple regression analysis revealed that age, gender, systolic blood pressure and insulin resistance independently accounted for 37% of the variability in albumin/creatinine ratios. When those 10 subjects with microalbuminuria and albumin/creatinine ratios greater than 3.5 were matched with 20 with normoalbuminuria for age, gender and body mass index, the microalbuminuric subjects had significantly lower LDL cholesterol/apo B ratios and a tendency to lower high density lipoprotein (HDL) cholesterol and HDL cholesterol/apo A1 ratios. Microalbuminuria is uncommon in the general population, and is related to ageing, blood pressure and other vascular risk factors. It may reflect the presence of established cardiovascular disease.

Lipoprotein (a) concentrations and apolipoprotein (a) phenotypes in normoglycaemic relatives of type 2 diabetic patients.

Serum lipoprotein (a) concentrations (Lp(a)) are largely under genetic control, and are strong predictors of coronary heart disease. It has been hypothesised that Lp(a) may contribute to the increased risk of coronary heart disease in familial Type 2 diabetes mellitus. We therefore examined the Lp(a) concentrations and the apolipoprotein (a) (apo(a)) phenotypes in 126 normoglycaemic first degree relatives from families with two or more living Type 2 diabetic patients. These were compared with 147 sex matched normoglycaemic control subjects with no family history of diabetes. Lp(a) concentrations were measured using an enzyme-linked immunosorbent assay (ELISA), and apo(a) isoforms were determined and classified according to the relative mobility of apo(a) on sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), relative to that of apolipoprotein B-100. There were no significant differences in Lp(a) concentrations between the relatives (R) and controls (C): 11.2 (R) vs. 11.1 (C) mg/dl (median). The distribution of apo(a) phenotypes was not significantly different between groups 0.65 (R) vs. 0.67 (C). These results show that first degree relatives at risk of developing Type 2 diabetes do not have abnormal Lp(a) concentrations or apo(a) phenotypes.

Lipoprotein composition and serum apolipoproteins in normoglycaemic first-degree relatives of non-insulin dependent diabetic patients.

Cardiovascular disease is the leading cause of death in non-insulin dependent diabetes mellitus and first degree relatives of such patients are at increased risk of developing diabetes and cardiovascular disease. The aim of the present study was to determine whether lipid abnormalities occur in normoglycaemic relatives of non-insulin dependent diabetic patients. Cholesterol, triglycerides, apolipoprotein A-I and apolipoprotein B concentrations were measured in serum; the lipoprotein fractions very low density, intermediate density, low density and high density lipoprotein were prepared by sequential flotation ultracentrifugation and their composition investigated. The groups were matched for age, sex and blood glucose concentrations although the relatives (n = 126) were more insulin resistant as determined using the homeostasis model assessment method [1.9 (0.8-9.0) vs 1.6 (0.4-4.9) mmol/mU per l (mean [95% confidence intervals]); p < 0.001] and had greater body mass indices [26.6 (4.1) vs 24.8 (3.9) (mean [S.D.]); p = 0.001] than control subjects (n = 126). Relatives had higher serum apolipoprotein B concentrations than control subjects [0.9 (0.3) vs 0.8 (0.3) g/l, p = 0.02) and lower serum apolipoprotein A-I concentrations (1.4 (0.3) vs 1.5 (0.3), p = 0.02). In multivariate linear regression analysis of all subjects log insulin resistance (p = 0.0001), age (p = 0.002) and waist:hip ratio (p = 0.01) were independent predicators of apolipoprotein B concentrations while waist:hip ratio (p < 0.001) and smoking status (p = 0.002) were independent predictors of apolipoprotein A-I concentrations. Lipoprotein composition (measured in a subgroup of 76 control subjects and 88 relatives), serum cholesterol and serum triglyceride concentrations did not differ between the groups. We conclude that atherogenic apolipoprotein abnormalities occur in normoglycaemic relatives of non-insulin dependent diabetic patients.

The effect of growth hormone replacement therapy for up to 12 months on lipoprotein composition and lipoprotein(a) in growth hormone-deficient adults.

The effect of growth hormone replacement therapy in near physiological doses on lipoprotein composition and serum lipoprotein(a) concentrations was investigated in growth hormone-deficient subjects. A randomised, double-blind, placebo-controlled trial of recombinant growth hormone was undertaken for 6 months followed by an open extension for a further 6 months (0.125 IU/kg per week for the first 4 weeks of each 6 month period and thereafter 0.25 IU/kg per week). A total of 18 patients with isolated growth hormone deficiency or hypopituitarism were studied. Lipid concentrations were estimated in lipoprotein fractions and protein concentrations were measured in low density lipoprotein (LDL). Glucose and glycated haemoglobin in blood and insulin, cholesterol, triglyceride, apolipoproteins A-I and B and lipoprotein(a) concentrations were measured in serum. In the placebo-controlled phase fasting blood glucose concentrations increased with growth hormone treatment from 5.0 +/- 0.2 to 5.8 +/- 0.2 mmol/l (P = 0.02) (mean +/- S.E.M.), although no significant changes were seen in lipids or lipoproteins. In the group receiving active treatment total serum cholesterol decreased from 6.0 +/- 0.4 to 5.2 +/- 0.3 mmol/l (P = 0.002) after 6 months, due to reduced LDL cholesterol concentrations. Low density lipoprotein protein concentrations fell (0.8 +/- 0.1 versus 0.7 +/- 0.1 g/l) (P = 0.005), and LDL phospholipid levels decreased from 0.9 +/- 0.1 to 0.7 +/- 0.1 mmol/l (P = 0.007). Serum cholesterol and LDL composition reverted to pre-treatment values by 12 months. Fasting blood glucose remained above pre-treatment values (P = 0.036) and fasting insulin was significantly increased (P = 0.044). There was no effect of growth hormone therapy on serum triglyceride, apolipoprotein or lipoprotein(a) concentrations. In conclusion, growth hormone therapy with near physiological doses has no long term effects on serum lipoprotein(a) concentrations or lipoprotein composition.

Reduced serum lipoprotein(a) levels in patients with primary biliary cirrhosis.

Lipoprotein(a) (Lp(a)) is a unique lipoprotein, elevated serum levels of which are independently associated with an increased risk of coronary heart disease (CHD). Primary biliary cirrhosis (PBC) is often associated with high serum cholesterol, itself a risk factor for CHD. Despite this, patients with PBC are thought to have a lower than expected incidence of CHD. We hypothesised that this may be related to low serum levels of Lp(a) in PBC patients. This was investigated by collecting fasting blood samples from 42 patients with PBC, 39 age- and sex-matched subjects with non-PBC liver disease and 432 community control subjects. Serum was analysed for total cholesterol, triglycerides, high density lipoprotein (HDL) cholesterol and apolipoproteins A1 and B (apo A1 and apo B). Lp(a) was measured by an enzyme-linked immunosorbent assay (ELISA) technique. There was a significant reduction of Lp(a) concentrations in the PBC group compared with the healthy controls (median value 28.5 mg/l vs. 75.0 mg/l, P < 0.005) and between the non-PBC liver disease group (median value 52.0 mg/l) and control group (P = 0.001). Within both the liver disease and PBC patient groups there were significant negative correlations between Lp(a) levels and bilirubin (R = -0.564, P < 0.001 and R = -0.395, P = 0.010 respectively). This preliminary study has demonstrated reduced Lp(a) levels in PBC patients which may be a contributory factor to explain a possible cardioprotective effect in such patients, despite elevated LDL cholesterol levels.

Elevated sodium-lithium countertransport: a familial marker of hyperlipidaemia and hypertension?

Erythrocyte sodium-lithium countertransport was measured in normolipidaemic and hyperlipidaemic hypertensive patients, hyperlipidaemic normotensive patients and normal controls. Hypertension and hyperlipidaemia were each independently associated with raised sodium-lithium countertransport (by analysis of variance, P less than 0.01 and P less than 0.01). The effects were additive so that hyperlipidaemia could not explain raised sodium-lithium countertransport in hypertension. In hyperlipidaemic hypertensive patients, levels of plasma cholesterol, triglycerides, low-density lipoprotein (LDL) cholesterol and very-low-density lipoprotein (VLDL) cholesterol were increased, and high-density lipoprotein (HDL) cholesterol was reduced. Of these patients, 73.3% had a known family history of hypertension. Their normotensive first degree relatives were studied, and 48% of these also had raised sodium-lithium countertransport and abnormal plasma lipids (raised cholesterol, triglycerides and LDL cholesterol, and reduced HDL cholesterol). Relatives with normal sodium-lithium countertransport had normal lipids. Therefore, raised sodium-lithium countertransport was associated with the inheritance of both hypertension and hyperlipidaemia, and this could explain why raised sodium-lithium countertransport has been associated with a family history of both hypertension and associated cardiovascular disease.

Plasma fibrinogen levels and fibrinogen genotype in non-insulin dependent diabetics.

The association between plasma fibrinogen levels, fibrinogen genotype, and the development of macrovascular disease was studied in 100 patients with non-insulin dependent diabetes mellitus (NIDDM). The mean plasma fibrinogen levels in patients with macrovascular disease was higher than those without, although the difference was not statistically significant (3.67 g l-1, and 3.43 g l-1, respectively). The frequency of the rare allele of the fibrinogen gene DNA polymorphism detected with the restriction enzyme Bc1I was slightly higher in the group of patients with disease, but the difference was not statistically significant (0.20 vs 0.16). The frequency of the TaqI polymorphism rare allele was the same in both groups (0.30 vs 0.31). However, the Bc1I polymorphism was strongly associated with plasma fibrinogen levels, with those patients heterozygous for the rare allele having mean levels 16 per cent higher than those lacking the allele (3.81 g l-1 vs 3.28 g l-1, p < 0.05). This data demonstrates that variation at the fibrinogen locus is involved in determining fibrinogen levels in patients with NIDDM, and suggests the possibility that fibrinogen genotype and plasma fibrinogen levels could be one of the factors making a small contribution to the development of macrovascular disease in diabetic patients.

Variation in the apolipoprotein B gene and development of type 2 diabetes mellitus.

Several studies have demonstrated an association between variation in the apolipoprotein (apo) B gene, principally as detected by the XbaI and EcoRI restriction fragment length polymorphisms (RFLPs), and lipoprotein levels or cardiovascular disease. We have examined the frequency of the EcoRI and XbaI RFLPs of the apoB gene in 95 white Type 2 diabetic patients aged between 45 and 80 years in order to ascertain whether variation in this gene may be influencing the development of Type 2 diabetes and associated atherosclerosis through obesity. Neither of the two RFLPs had a significant association with clinically defined cardiovascular disease or with body mass index in our sample. However, while XbaI displayed no association with circulating levels of lipids, lipoproteins or apolipoproteins, the presence of the rare (R2) alele of EcoRI (absence of cutting site) was associated with significantly higher levels of circulating triglycerides. Furthermore, the EcoRI R2 allele was over-represented in the diabetic sample when compared to a healthy control group. Our findings support previous studies which have shown an effect of variation at the apoB gene on circulating lipid levels; additionally, variation in this gene may contribute to the development of Type 2 diabetes mellitus.

Laboratory facilities for investigating lipid disorders in the United Kingdom: results of the British Hyperlipidaemia Association survey.

AIMS: To determine the availability of facilities for the investigation of hyperlipidaemia in the United Kingdom. METHODS: A questionnaire was sent to all health districts in the United Kingdom. RESULTS: The response rate was 81%. All laboratories used enzymatic techniques to measure serum triglyceride and cholesterol concentrations, although there were differences in standardisation procedures. Reference ranges for serum lipids were quoted by 58% of laboratories while 50% quoted "desirable limits". Almost half specified that fasting blood samples were required. High density lipoprotein cholesterol concentrations were estimated by 75% and apolipoproteins AI and B by 14% of laboratories; there were differences in specimen type and considerable diversity in procedures used for measurement. CONCLUSIONS: Many laboratories were unaware of current recommendations for screening for hypercholesterolaemia in the community. The present survey indicated an urgent need for the introduction of better reference methods, standardisation, and quality assurance procedures before apolipoproteins become a routine part of coronary heart disease risk assessment.

Plasma oxalate concentration and secondary oxalosis in patients with chronic renal failure.

To examine the association between hyperoxalaemia and secondary oxalosis, measurement of plasma oxalate concentration was combined with a search for tissue deposition of calcium oxalate crystals in patients with chronic renal disease. Two groups of patients were studied. In the first, samples of the inferior epigastric artery were taken from 35 patients at the time of renal transplantation. In the second, sections taken at necropsy from 23 patients with chronic renal failure in whom plasma oxalate had been measured before death were examined. Though plasma oxalate concentrations ranged between 6 and 116 mumol/l (four to 78 times greater than the upper limit of the reference range), no extrarenal deposits of oxalate were found in either study. Renal deposition of oxalate was associated with a plasma oxalate concentration of greater than 20 mumol/l. This study gives no support to the suggestion that hyperoxalaemia of the degree seen in patients with the type of chronic renal failure that is not due to primary hyperoxaluria confers an appreciable risk of extrarenal oxalosis.

Effect of storage at -70 degrees C on lipid, lipoprotein and apolipoprotein concentrations.

We have investigated the effects on lipid, apolipoprotein and lipoprotein measurements of storing unfractionated serum from normolipidaemic and hyperlipidaemic subjects at -70 degrees C for 10 days, 3 months and 6 months. Total serum concentrations of lipids and apolipoproteins were stable except for triglyceride concentrations. These increased on storage although the change was < 2.0% after 6 months. Storage of serum before sequential flotation ultracentrifugation resulted in decreased free cholesterol and phospholipid concentrations in very low density lipoproteins. In low density lipoproteins, free cholesterol concentrations increased and protein concentrations decreased on storage, while esterified cholesterol and phospholipid concentrations fell after 10 days but did not differ from baseline concentrations after storage for 6 months. Within high density lipoproteins, there were decreases in triglyceride and protein concentrations. Although storage of serum at -70 degrees C for up to 6 months did not result in extensive changes in most lipoprotein fractions, separation of lipoprotein fractions from serum should, ideally, be performed as soon as possible after collection.

The determination of plasma oxalate concentrations using an enzyme/bioluminescent assay.

An enzyme/bioluminescent assay for the determination of oxalate in plasma is described in which NADH, a reaction product of the enzymic degradation of oxalate by oxalate decarboxylase and formate dehydrogenase, is determined using a commercially available bioluminescent system. In contrast to most previously documented methods, this sensitive and specific assay requires minimal sample preparation allowing oxalate concentrations to be determined within 2 h of sample collection. The limit of detection for plasma samples is 0.8 mumol/l. The recovery of oxalate added to plasma averaged 99%. The inter-batch coefficient of variation, calculated by analysis of a plasma sample from a uraemic patient (oxalate concentration = 45.8 mumol/l) on 8 occasions, over a period of 5 wk, was 3.2%. Plasma oxalate concentrations in 35 normal subjects ranged from less than 0.8-1.5 mumol/l, which is in excellent agreement with values obtained by in vivo isotope dilution studies. Plasma oxalate was found to be strikingly elevated in a group of uraemic patients maintained on regular haemodialysis.

Effects of isotretinoin on serum lipids and lipoproteins, liver and thyroid function.

Seven patients with severe rosacea were treated with 1 mg/kg per day isotretinoin for 12 wk. There were significant increases in serum triglyceride (p less than 0.001) and cholesterol (p less than 0.001). Triglyceride associated with very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL) increased (p less than 0.01), cholesterol in VLDL and LDL increased (p less than 0.01), and levels of HDL cholesterol decreased (p less than 0.01). There were changes in indices of liver function, with increased levels of gamma-glutamyltransferase (GGT) (p less than 0.01), alkaline phosphatase (ALP) (p less than 0.01) and aspartate aminotransferase (AST) (p less than 0.01), and decreased bilirubin levels (p less than 0.05). Although levels of thyroxine and triiodothyronine were lower after treatment (p less than 0.05), there were no changes in basal levels of thyroid-stimulating hormone (TSH), luteinizing hormone (LH) or follicle-stimulating hormone (FSH), and responses to thyrotrophin releasing hormone (TRH) and luteinizing hormone releasing hormone (LHRH) were unchanged. These changes may partially be explained by induction of hepatic microsomal enzymes by isotretinoin.

Serum triglyceride and insulin levels are associated with erythrocyte sodium-lithium counter-transport activity in normoglycaemic individuals.

The relationship between erythrocyte sodium-lithium counter-transport activity, serum insulin, lipids and demographic factors was examined in 93 normoglycaemic predominantly normotensive individuals with mild fasting hypercholesterolaemia (greater than 5.2 mmol/l). The major significant univariate correlates of sodium-lithium counter-transport activity were fasting serum triglycerides, HDL cholesterol, the ratio of fasting glucose: insulin, apo A1, alcohol consumption and apo B. Stepwise multiple regression analysis revealed 24% of the variability in sodium-lithium counter-transport activity could be accounted for by independent contributions of fasting serum triglycerides, alcohol consumption, the fasting glucose/insulin ratio and apo A1 and ANOVA confirmed a significant relationship with fasting insulin measures that was independent of serum triglycerides (P less than 0.05). The relationship between erythrocyte sodium-lithium counter-transport activity and concentrations of serum triglycerides, HDL components, insulin and additionally alcohol consumption, could reflect the influence of those variables on erythrocyte structure and function.

A simple, sensitive technique for classification of apolipoprotein(a) isoforms by sodium dodecyl sulphate-polyacrylamide gel electrophoresis.

Lipoprotein(a) (Lp(a)) is a lipoprotein containing a unique glycoprotein, apolipoprotein(a) (apo(a)), which shows considerable heterogeneity of apparent molecular mass on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). A unifying classification of isoform has been lacking. A simple sensitive procedure for classifying apo(a) isoforms was developed in which the relative mobility of apo(a) on SDS-PAGE was related to that of apolipoprotein (apo) B-100 (Rf vs B). After Western blotting apo(a) bands were visualised by a sensitive double antibody technique employing commercial polyclonal antibodies (sheep antihuman Lp(a) antibody, alkaline phosphatase-linked donkey antisheep antibody). The technique was sensitive (lower limit of detection 0.02 micrograms apo(a)) and had good reproducibility (coefficient of variation 0.9-6.4%). Ten isoform mobilities are described (less than 0.35, 0.40, 0.50, 0.60, 0.70, 0.80, 1.0, 1.10, greater than 1.15). Individuals may have single or double band phenotypes. This classification is compatible with those previously described and the method is suitable for many laboratories, as it employs standard equipment and commercially available materials.