Practical approaches to the detection of macrotroponin

INTRODUCTION

Macrotroponin is increasingly recognised as a cause of confusion in interpreting high-sensitivity cardiac troponin (hs-cTnI) results. In this study, we sought to evaluate two practical approaches to detecting macrotroponin. These two approaches are PEG precipitation and SVM (support vector machine) analysis to classify discrepancies between hs-cTn assays.

METHOD

Residual serum and heparin plasma specimens (n = 483) with initially elevated hs-cTnI from hospital and community laboratories were retested on multiple hs-cTn platforms before and after PEG precipitation and Protein A immunoglobulin depletion. SVM analysis was conducted to identify a linear equation that best discriminated specimens with macrotroponin using a combination of results from two different hs-cTn assays.

FINDINGS

The diagnostic performance of PEG precipitation was carried out using Protein A immunoglobulin depletion as the reference comparator. When a cutoff residual activity after PEG precipitation of ≤ 20% was used, this threshold carried a high specificity of 92% (confidence interval 83-98%; n = 189) using the Siemens hs-cTnI Vista assay and 95% specificity (86%-98%; n = 242) using the Abbott hs-cTnI Architect assay. SVM analysis generated a linear equation identifying macrotroponin specimens from results obtained on two hs-cTn assays. This approach can be highly specific, comparable to PEG precipitation when certain assay combinations and concentrations are used.

CONCLUSION

We describe and identify practical alternatives to detecting macrotroponin. These approaches can be optimised for high specificity, reducing the need for more complex laboratory methods.

Effect of Macrotroponin in a Cohort of Community Patients with Elevated Cardiac Troponin

BACKGROUND

Macrotroponin is an important cause of discrepancy between current high-sensitivity cardiac troponin (hs-cTn) assays, however, its clinical significance is unclear. This study examined the effects of macrotroponin and repeat testing by different hs-cTnI assays in a cohort of community patients with elevated hs-cTnI.

METHODS

The first residual serum specimen from each patient in the community admitted to hospital with elevated hs-cTnI (Siemens hs-cTnI Centaur) was retested after immunoglobulin depletion and by 5 other hs-cTn assays. Low recovery of cTnI (<40%) following immunoglobulin depletion was considered as macrotroponin. A retrospective chart review was performed for these participants. Investigator-adjudicated diagnosis served as the reference standard.

RESULTS

In our cohort of community patients with elevated troponin (n = 188), participants with macrotroponin (n = 99) often had a multifactorial or indeterminate myocardial injury (56% vs 25%) and were less likely to have acute coronary syndrome (9% vs 28%). On repeat testing of cTn on other platforms, better diagnostic performance (c-statistics) for ischemic and non-ischemic cardiac causes was observed on the Beckman Access hs-cTnI (0.74; 95% confidence interval [CI] 0.67-0.81) or the Abbott hs-cTnI Architect (0.75; CI 0.68-0.82) compared to the Siemens hs-cTnI Vista (0.62; CI 0.54-0.70; P < 0.05). This could be attributed to differences in assay reactivity for macrotroponin. Interestingly, better diagnostic performance was observed in patients without macrotroponin. Although a small number of deaths occurred (n = 16), participants with macrotroponin had better overall survival.

CONCLUSIONS

In the low-risk setting, the presence of macrotroponin was clinically associated with multifactorial or indeterminate causes of troponin elevation.

Identification of macrotroponin T: findings from a case report and non-reproducible troponin T results

OBJECTIVES

Macrotroponin is due to cardiac troponin (cTn) binding to endogenous cTn autoantibodies. While previous studies showed a high incidence of macrotroponin affecting cTnI assays, reports of macrotroponin T, particularly without cTnI reactivity, have been rare. Although the clinical significance of macrotroponin is not fully understood, macroenzymes and complexes are recognised to cause confusion in interpretation of laboratory results. The potential for adverse clinical consequences due to misinterpretation of affected results is very high.

METHODS

We describe four cases of macrotroponin T with persistently low high sensitivity cTnT (hs-cTnT) by the 9 min compared to the 18 min variant of the assay. Three cases were serendipitously identified due to the use of a lot number of Roche hs-cTnT affected by non-reproducible results, necessitating measurement of cTnT in duplicate. We identified and characterised these macrotroponin specimens by immunoglobulin depletion (Protein A and PEG precipitation), mixing studies with EDTA and recombinant cTnT.

RESULTS

In cases of macro-cTnT, a lower result occurred on the hs-cTnT using the 9 min compared to 18 min variant assay (ratio of 9-18 min hs-cTnT <0.80). Mixing studies with recombinant cTnT or EDTA demonstrated a difference in recovery vs. controls. One of these patients demonstrated a high molecular weight complex for cTnI and cTnT demonstrating a macrocomplex involving both cTn. This patient demonstrated a rise and fall in cTn when measured by several commercial assays consistent with genuine acute cardiac injury.

CONCLUSIONS

We identified several cases of macro-cTnT and described associated clinical and biochemical features.

Effect of macrotroponin on the utility of cardiac troponin I as a prognostic biomarker for long term total and cardiovascular disease mortality

Macrotroponin is a complex formed between endogenous cardiac troponin autoantibodies and circulating cardiac troponin (cTn). It is a recognised cause of discrepancy between current high sensitivity troponin (hs-cTn) assays; and immunoglobulin-bound (macrotroponin) and unbound cTn can coexist in varying proportions in the acute setting. Increasingly it is considered when laboratory cTn results do not match a patient's clinical picture. However, despite the better understanding of macrotroponin as an analytical interference, its clinical significance remains unclear. The aim of this study was to determine the potential impact of macrotroponin on the use of cTn as a long-term prognostic marker. We repeated cTnI testing after polyethylene glycol (PEG) precipitation on consecutive participants (n=159) with a first elevated cTn above 0.2 μg/L during their hospital admission episode. Because this paper is looking at outcomes in years, the initial data were generated at a time when non-hs-cTn assays were in use. We divided the cohort into two groups based on an exploratory PEG recovery cut-off of <34.6% to indicate the presence of possible macrotroponin and compared the overall and cardiovascular related mortality. The median follow-up time for the overall cohort was 8.35 years (8.32-8.40 interquartile range) with no difference between the two groups. The overall median survival was 8.1 years. Our findings indicate a hazard ratio of 0.54 (0.32-0.91 95% CI) for all-cause mortality and 0.48 (0.24-0.95) for cardiovascular mortality in patients with possible macrotroponin compared to those patients with troponin elevation without evidence of macrotroponin, after adjustment for common cardiovascular disease risk factors. Furthermore, an association was observed between PEG% recovery and all-cause mortality (p<0.05). This study showed that patients with macrotroponin have comparatively favourable long-term all-cause and cardiovascular mortality in a cohort of patients with elevated troponin. We illustrate the importance of recognising cTn results as being a summation of heterogeneous components, including those bound to antibodies, and the potential role of macrotroponin to further improve our interpretation and use of cTn as a biomarker.

Kavain Interference with Amphetamine Immunoassay

INTRODUCTION

We encountered unexpected false positive urine results in three patients for amphetamine-type substances by immunoassay, measured as part of community drug prevention programmes. Kavain was identified in all three urine samples by gas chromatography mass spectrometry (GC-MS). No other potential cross-reactants were found.Kavain is a kava-lactone present in kava, a ceremonial and recreational drink derived from roots and stem of the plant Piper Methysticum. It is consumed regularly by many indigenous Pacific and Australian Aboriginal communities.

METHODS

Urine immunoassay was performed on a Beckman Coulter AU480 Analyser using CEDIA amphetamine-type substances reagent and DRI ethanol reagent. Three different kava powders were purchased from local kava clubs and dissolved in ethanol, then evaporated and reconstituted in blank urine and analysed by immunoassay, GC-MS for amphetamine-type substances. Additionally authentic kavain standard was also tested for cross reactivity by immunoassay and analysed by GC-MS to compare the mass fragmentation pattern and retention time with the kava powder and patient specimens.

RESULTS AND DISCUSSION

The patient urine samples tested positive by CEDIA immunoassay for amphetamines. However, when analysed by GCMS they were negative for amphetamine-type but contained kavain.The kava powders and kavain standard all cross reacted with the amphetamine immunoassay to give falsely detected results. GCMS did not identify any amphetamine-type compounds in any of the Kava powders nor in the kavain standard.

CONCLUSION

To our knowledge, this is the first report of false positive amphetamine measurements due to kavain, a component of the kava drink, widely consumed in Oceania and Australasia.

Discrepancy between Cardiac Troponin Assays Due to Endogenous Antibodies

BACKGROUND

Despite well-described analytical effects of autoantibodies against cardiac troponin (cTn) I on experimental assays, no study has systematically examined their impact on cTn assays in clinical use. We determined the effects of endogenous antibodies on 5 different cTnI assays and a cTnT assay.

METHODS

cTn was measured by 6 methods: Siemens hs-cTnI Centaur, Siemens hs-cTnI Vista, Abbott hs-cTnI Architect, Beckman hs-cTnI Access, Beckman cTnI Access, and Roche hs-cTnT Elecsys. Measurements were repeated on 5 assays (all except Siemens hs-cTnI Vista) following immunoglobulin depletion by incubation with protein A. Low recovery of cTnI (<40%) following immunoglobulin depletion was considered positive for macro-cTnI. Protein A findings were validated by gel filtration chromatography and polyethylene glycol precipitation.

RESULTS

In a sample of 223 specimens selected from a community laboratory that uses the Siemens hs-cTnI Centaur assay and from which cTn was requested, 76% of samples demonstrated increased cTnI (median, 88 ng/L; interquartile range, 62-204 ng/L). Macro-cTnI was observed in 123 (55%) of the 223 specimens. Comparisons of cTnI assays markedly improved once patients with macro-cTnI were removed. Passing-Bablok regression analysis between hs-cTnI assays demonstrated different slopes for patients with and without macro-cTnI. In patients with macro-cTnI, 89 (72%) showed no effect on the recovery of cTnT, whereas 34 (28%) had reduced recovery of cTnT. The proportion of results above the manufacturers' 99th percentile varied with the cTn assay and macro-cTnI status.

CONCLUSION

We suggest that the observed discrepancy between hs-cTnI assays may be attributed in part to the presence of macro-cTnI.

A three-way comparison of glycated haemoglobin: are results from the three platforms interchangeable?

AIMS

To determine whether glycated haemoglobin (HbA1c) results from three commonly used platforms can be interpreted cumulatively and used interchangeably in individuals with common haemoglobinopathies. A secondary goal was to assess the relationship between HbA1c concentrations, and haemoglobin and mean corpuscular volume in this population.

METHODS

One hundred and forty-five samples, mostly with haemoglobinopathies, were tested by each of: Roche Gen.3 Cobas c513, Capillarys 2 Flex-Piercing and Bio-Rad D-100 platforms. Statistical comparisons and limits of performance based on biological variation, international recommendations, and local diagnostic cut-offs were drawn upon to determine comparability of results.

RESULTS

Inter-platform measurements were not significantly different for the large majority of results. The four HbA1c results that showed maximum discrepancy between triplicates had the following abnormalities: heterozygous haemoglobin S/ beta thalassemia, heterozygous haemoglobin S/ alpha thalassemia, beta thalassemia trait and alpha thalassemia trait. Six triplicates of results in the thalassemia groups (7.5% of thalassemia samples) had levels that misclassified patients' glycaemic status. There was no correlation between HbA1c concentration and mean corpuscular volume, and a weak negative correlation between HbA1c concentration and haemoglobin concentration.

CONCLUSION

HbA1c concentrations measured by Cobas c513, Capillarys 2 Flex-Piercing and the Bio-Rad D-100 were found to be comparable in the large majority of samples. While discordance was due to assay imprecision in some cases, in others no biological or analytical explanation could be found.

The decision to discontinue screening for carnitine uptake disorder in New Zealand

When screening for carnitine uptake disorder (CUD), the New Zealand (NZ) newborn screening (NBS) service identified infants as screen-positive if they had initial and repeat free carnitine (C0) levels of less than 5.0 μmol/L. Since 2006, the NBS service has identified two infants with biochemical and genetic features consistent with neonatal CUD and nine mothers with features consistent with maternal CUD. A review of the literature suggests that these nine women reflect less than half the true prevalence and that CUD is relatively common. However, the NZ results (two infants) suggest a very low sensitivity and positive predictive value of NBS. While patients presenting with significant disease due to CUD are well described, the majority of adults with CUD are asymptomatic. Nonetheless, treatment with high-dose oral L-carnitine is recommended. Compliance with oral L-carnitine is likely to be poor long term. This may represent a specific risk as treatment could repress the usual compensatory mechanisms seen in CUD, such that a sudden discontinuation of treatment may be dangerous. L-carnitine is metabolized to trimethylamine-N-oxide (TMAO) and treated patients have extremely high plasma TMAO levels. TMAO is an independent risk factor for atherosclerosis and, thus, caution should be exercised regarding long-term treatment with high-dose carnitine of asymptomatic patients who may have a biochemical profile without disease. Due to these concerns, the NZ Newborn Metabolic Screening Programme (NMSP) initiated a review via a series of advisory and governance committees and decided to discontinue screening for CUD.

Falsely elevated plasma metanephrine in patients taking midodrine

Plasma metanephrines have become the biochemical test of choice for suspected phaeochromocytomas and paragangliomas in many institutions. We encountered two separate cases of significantly elevated plasma metanephrines in patients taking midodrine, a sympathomimetic drug used in the treatment of severe postural hypotension, in the absence of a diagnosis of phaeochromocytomas and paragangliomas. Upon stopping midodrine treatment, plasma metanephrine concentrations returned to normal in both patients. To explore the hypothesis that midodrine or its metabolite desglymidodrine might interfere with the metanephrines assay, we tested the interaction of midodrine with metanephrine assays from two different centres. High-performance liquid chromatography tandem mass spectrometry on plasma samples and on methanolic extract of midodrine demonstrated co-elution of the metabolite desglymidodrine with metanephrine. We conclude that patients taking midodrine may have falsely elevated plasma metanephrine as a result of analytical interference, and clinicians need to be aware of this problem.

Utilization of Reflex Testing for Direct Bilirubin in the Early Recognition of Biliary Atresia

BACKGROUND

Delayed diagnosis of biliary atresia is an important cause of pediatric end-stage liver failure and liver transplantation. We sought to determine whether direct bilirubin is underutilized by retrospectively reviewing patients with biliary atresia. Further, we aimed to determine the role of reflex testing for direct bilirubin in patients suspected for jaundice.

METHODS

The time intervals between total bilirubin and direct bilirubin measurements were retrospectively reviewed in patients with biliary atresia. We also audited the results of two major laboratories that had implemented reflex testing for direct bilirubin. We evaluated the clinical impact and cost of reflex testing in infants with increased direct bilirubin (&gt;1.5 mg/dL; &gt;25 μmol/L).

RESULTS

In patients with known biliary atresia, an isolated total bilirubin measurement preceded direct bilirubin measurement in 46% (40/87) of patients; with a median delay of 19 days (interquartile range 3–44 days). In the community setting, direct bilirubin had a higher clinical specificity for biliary atresia than in the hospital setting. Reporting direct bilirubin results in 1591 infants younger than 2 weeks of age in the community was associated with three admissions to the hospital, one of whom was diagnosed with biliary atresia. The cost for the two laboratories for direct-bilirubin testing was estimated at US$3200 (NZ$4600) for each newly diagnosed case of biliary atresia.

CONCLUSIONS

We identified underutilization of direct bilirubin as a cause of delay in the recognition of biliary atresia and show that reflex testing for direct bilirubin in jaundiced infants is a cost-effective solution.

The Risk of Fatty Acid Oxidation Disorders and Organic Acidemias in Children with Normal Newborn Screening

New Zealand has undertaken expanded newborn screening since 2006. During that period there have been no reported cases of fatty acid oxidation disorders or organic acidemias that have been diagnosed clinically that the screening programme missed. However there may have been patients that presented clinically that were not diagnosed correctly or notified.In order to investigate the false-negative screening rate a case-control study was undertaken whereby the clinical coding data and relevant medical records were reviewed for 150 controls and 525 cases. The cases had normal newborn screening but with key analytes and/or ratios just below the notification level for individual disorders and thus in theory were most at risk of having metabolic disease.Two cases had medical histories suggestive of metabolic disease and thus could represent a false-negative screen. One of these had marginally elevated octanoyl carnitine levels and thus possible medium-chain acyl Co-A dehydrogenase deficiency (MCADD) while the other had elevated isovaleryl carnitine and thus may have been a case of isovaleric acidemia (IVA). However, subsequent molecular analysis revealed that the diagnosis of MCADD and IVA was unlikely.Despite relatively high cut-offs the New Zealand Newborn Metabolic Screening Programme does not appear to have missed any confirmed cases of fatty acid oxidation disorders and organic acidemias in its first 8 years of expanded newborn screening. This would suggest a similar low false-negative screening rate in centres with comparable screening protocols and would indicate that the risk of fatty acid oxidation disorders and classical organic acidemias in children who had normal newborn screening is low.

Reproduction Symposium: does grazing on biosolids-treated pasture pose a pathophysiological risk associated with increased exposure to endocrine disrupting compounds?

Biosolids (processed human sewage sludge), which contain low individual concentrations of an array of contaminants including heavy metals and organic pollutants such as polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), and polychlorinated dibenzodioxins/polychlorinated dibenzofurans known to cause physiological disturbances, are increasingly being used as an agricultural fertilizer. This could pose a health threat to both humans and domestic and wild animal species. This review summarizes results of a unique model, used to determine the effects of exposure to mixtures of environmentally relevant concentrations of pollutants, in sheep grazed on biosolids-treated pastures. Pasture treatment results in nonsignificant increases in environmental chemical (EC) concentrations in soil. Whereas EC concentrations were increased in some tissues of both ewes and their fetuses, concentrations were low and variable and deemed to pose little risk to consumer health. Investigation of the effects of gestational EC exposure on fetal development has highlighted a number of issues. The results indicate that gestational EC exposure can adversely affect gonadal development (males and females) and that these effects can impact testicular morphology, ovarian follicle numbers and health, and the transcriptome and proteome in adult animals. In addition, EC exposure can be associated with altered expression of GnRH, GnRH receptors, galanin receptors, and kisspeptin mRNA within the hypothalamus and pituitary gland, gonadotroph populations within the pituitary gland, and regional aberrations in thyroid morphology. In most cases, these anatomical and functional differences do not result in altered peripheral hormone concentrations or reproductive function (e.g., lambing rate), indicating physiological compensation under the conditions tested. Physiological compensation is also suggested from studies that indicate that EC effects may be greater when exposure occurs either before or during gestation compared with EC exposure throughout life. With regard to human and animal health, this body of work questions the concept of safe individual concentration of EC when EC exposure typically occurs as complex mixtures. It suggests that developmental EC exposure may affect many different physiological systems, with some sex-specific differences in EC sensitivity, and that EC effects may be masked under favorable physiological conditions.

Long term temporal and spatial changes in the distribution of polychlorinated biphenyls and polybrominated diphenyl ethers in Scottish soils

Long term changes in polychlorinated biphenyl (PCB) and polybrominated diphenyl ether (PBDE) concentrations in soil from four transects across Scotland were measured in three surveys conducted between 1990 and 2007-9. Overall PCB level declined during this period (22.5 to 4.55 ng/g, p<0.001) but PBDEs increased (0.68 to 2.55 ng/g, p<0.001), reflecting the ban on PCB use in the 1980s while PBDE use increased until about 2004 when the use of penta-mix congener ceased in Europe. The proportion of lighter PCB congeners (28+52) present declined (p<0.001) primarily between 1990 and 1999. However, the proportion of lighter PBDE congeners (47+99) in the soil samples increased (p<0.01) from 1990 to 1999 and declined (p<0.001) thereafter, probably reflecting the introduction of legislation banning penta-BDE products and the degradation of lighter congeners and their translocation. PCBs were slightly higher in two southernmost transects but PBDE concentrations were significantly higher (p<0.001) in the two southern transects than in the two northern transects. This may reflect proximity to areas of high population and industrial activity. It is concluded that temporal and spatial changes in the distribution of PCBs and PBDEs reflect geography, physical processes and legislation.

Effects of calcium supplementation on lipids, blood pressure, and body composition in healthy older men: a randomized controlled trial

BACKGROUND

Calcium supplementation has been suggested to have beneficial effects on serum lipids, blood pressure, and body weight, but these possibilities have not been rigorously assessed in men.

OBJECTIVE

This study evaluated the effect of calcium supplementation on the change in the ratio of HDL to LDL cholesterol (primary endpoint) and on changes in cholesterol fractions, triglycerides, blood pressure, and body composition (secondary endpoints).

DESIGN

We carried out a randomized controlled trial of calcium supplementation in 323 generally healthy men over a period of 2 y. Subjects were randomly assigned to take placebo, 600 mg Ca/d, or 1200 mg Ca/d.

RESULTS

There was no significant treatment effect on the ratio of HDL to LDL cholesterol (P = 0.47) nor on weight, fat mass, lean mass, triglycerides, or total, LDL, or HDL cholesterol (P > 0.28 for all). There were downward trends in systolic and diastolic blood pressures within the calcium-supplemented groups, but there were no significant treatment effects over the whole trial period (P > 0.60). In a post hoc analysis of those with baseline calcium intakes below the median value (785 mg/d), blood pressures showed borderline treatment effects (P = 0.05-0.06 for changes at 2 y in those who received 1200 mg Ca/d compared with placebo: systolic, -4.2 mm Hg; diastolic, -3.3 mm Hg). Low magnesium intake showed a similar interaction. No treatment effects on weight or body composition were found.

CONCLUSIONS

These data do not show significant effects of calcium supplementation on serum lipids or body composition. Calcium supplementation in those with low dietary intakes may benefit blood pressure control. This trial was registered with the Australian Clinical Trials Registry as ACTRN 012605000274673.

A randomised, double-blind study comparing lumiracoxib with naproxen for acute musculoskeletal pain

BACKGROUND

Some selective cyclooxygenase-2 (COX-2) inhibitors have been shown to provide analgesic efficacy in patients with acute pain.

AIM

To compare the efficacy and safety of the COX-2 inhibitor lumiracoxib 400 mg once daily (qd) and naproxen 500 mg twice daily (bid) in patients with acute musculoskeletal pain caused by uncomplicated soft tissue injury.

METHODS

This was a randomised, double-blind, parallel-group, non-inferiority study set in 39 primary care centres in the UK. Patients were randomised to lumiracoxib 400 mg qd or naproxen 500 mg bid and took the study medication for as long as they felt that it was needed, up to day 7. The primary efficacy analysis was the sum of the pain intensity difference (0-100 mm visual analogue scale) determined morning and evening over the first 5 days of treatment (SPID-5).

RESULTS

The intention-to-treat population comprised 406 patients [lumiracoxib 400 mg qd (n = 207); naproxen 500 mg bid (n = 199)]. Both treatments were effective in reducing pain intensity over 5 days. The mean SPID-5 scores were 117.0 mm.day for lumiracoxib and 118.2 mm.day for naproxen [the treatment difference based on adjusted means from the ANCOVA was -2.78 mm.day, 95% confidence interval (CI) -17.4, 11.9]. The lower margin of the 95% CI was above the predetermined non-inferiority margin (-50 mm.day) for SPID-5, indicating non-inferiority of lumiracoxib compared with naproxen. Both treatments were well tolerated.

CONCLUSION

Lumiracoxib 400 mg qd is as effective as naproxen 500 mg bid for the management of moderate-to-severe acute musculoskeletal pain.

Personal impact of type 2 diabetes decreased over 5 years: implications for motivating patients

AIM

To investigate the change in personal impact of diabetes, in the same patients, over 5 years.

METHODS

Subjects were 144 Europeans and 63 Polynesians. Personal impact was measured by closed questions asking if diabetes affected work, interests, home life, social life and home relationships.

RESULTS

After 5 years participants had deteriorated metabolic measures and more frequent and severe complications. Nevertheless, the personal impact from having any problem caused by diabetes reduced by 60%. Knowledge of diabetes and self-blood glucose monitoring had improved. People were more likely to accept their diagnosis and were less concerned if others knew. They wanted to know more about diabetes, they felt more in control of the condition and found food restrictions less onerous, but were more worried by their diabetes.

CONCLUSION

Personal impact of diabetes decreased over 5 years. This and associated attitudinal changes, probably explained by 'response shift', produce both challenges and opportunities for clinicians seeking to educate and motivate patients. We need to ask patients directly rather than presume how diabetes is impacting on their life. Only then can we construct joint knowledge with our patients in ways that are personalized to their current attitudes and concerns.

The anti-oestrogen tamoxifen produces haemodilution in normal postmenopausal women

OBJECTIVES

To report the effects of the anti-oestrogen tamoxifen on biochemical and haematological parameters.

DESIGN

Randomized, double-blind comparison of tamoxifen 20 mg per day and placebo, over two years.

SETTING

A university hospital.

SUBJECTS

Forty-six healthy late-postmenopausal women (mean, SD time since menopause; 11, seven years).

MAIN OUTCOME MEASURES

Blood specimens were drawn in the fasting state at baseline, six months and two years for measurement of haemoglobin, haematocrit, erythrocyte mean cell volume, mean erythrocyte haemoglobin, leucocyte count, platelet count, urea, electrolytes, creatinine and albumin.

RESULTS

There was a significant decline in the haemoglobin concentration in the tamoxifen group (-4.4, 1.2 g/L; mean, SE) and its levels were lower in this group than in those receiving placebo (P = 0.004). Similarly, haematocrit, erythrocyte count and total leucocyte count were lower in those on placebo (P = 0.002, P = 0.01 and P = 0.01, respectively) and platelet count showed a similar trend (P = 0.08). In the tamoxifen group, the level of serum albumin fell significantly (-2.2, 0.4 g/L) and was lower throughout the study than that in the placebo group (P = 0.006). That of serum urea tended to fall (-0.4, 0.2 mmol L) but the between-groups comparison was not significant (P = 0.18).

CONCLUSIONS

These data suggest that tamoxifen exerts a haemodilutory effect in normal postmenopausal women. Since a similar effect has been reported in response to postmenopausal oestrogen therapy, it is likely that the observed changes represent another oestrogenic effect of tamoxifen in postmenopausal women. Haemodilution may contribute to the reduced incidence of cardiovascular disease reported in tamoxifen-treated women, and, therefore, its assessment in the new oestrogen agonists/antagonists being developed for cardiovascular disease prevention may be important.

Selective modulation of the expression of L-selectin ligands by an immune response

BACKGROUND

The adhesion molecule L-selectin is expressed on the cell surface of lymphocytes and mediates their migration from the bloodstream into lymph nodes. L-selectin is able to recognize four glycoprotein ligands, three of which--Sgp50, Sgp90, and Sgp200--are sulphated, bind specifically to L-selectin and are synthesized by the high endothelial venules of the peripheral and mesenteric lymph nodes. One of these three sulphated L-selectin ligands, Sgp90, has been shown to be identical to the known surface marker CD34 and is expressed on the cell surface of endothelial cells. The cDNA encoding Sgp50 has been cloned, and its product, which has been designated GlyCAM-1, is secreted. The third ligand, Sgp200, is both secreted and cell-associated. We have investigated how the expression of these sulphated glycoproteins is regulated during an immune response.

RESULTS

Here we demonstrated that, during a primary immune response, the expression and secretion of both GlyCAM-1 and Sgp200 are reduced, recovering to normal levels 7-10 days after antigen stimulation. In contrast, the expression of cell-associated CD34 and Sgp200 is relatively unaffected. These results may account for the modest decreases in the binding of an L-selectin-IgG fusion protein to high endothelial venules of inflamed peripheral lymph nodes that have been observed after antigen exposure. In vivo experiments show that, following the decrease in the levels of secreted GlyCAM-1 and Sgp200, migration of lymphocytes from the blood stream into lymph nodes remains L-selectin-dependent, but more lymphocytes home to antigen-primed than unprimed peripheral lymph nodes.

CONCLUSIONS

We suggest that the secreted forms of the L-selectin ligands GlyCAM-1 and Sgp200 act as modulators of cell adhesion, and that cell-associated CD34 and Sgp200 are the ligands that mediate the initial loose binding of lymphocytes to high endothelial venules.

Global vascular expression of murine CD34, a sialomucin-like endothelial ligand for L-selectin

Extravasation of leukocytes into organized lymphoid tissues and into sites of inflammation is critical to immune surveillance. Leukocyte migration to peripheral lymph nodes (PLN), mesenteric lymph nodes (MLN) and Peyer's patches (PP) depends on L-selectin, which recognizes carbohydrate-bearing, sialomucin-like endothelial cell surface glycoproteins. Two of these ligands have been identified at the molecular level. One is the potentially soluble mucin, GlyCAM 1, which is almost exclusively produced by high endothelial venules (HEV) of PLN and MLN. The second HEV ligand for L-selectin is the membrane-bound sialomucin CD34. Historically, this molecule has been successfully used to purify human pluripotent bone marrow stem cells, and limited data suggest that human CD34 is present on the vascular endothelium of several organs. Here we describe a comprehensive analysis of the vascular expression of CD34 in murine tissues using a highly specific antimurine CD34 polyclonal antibody. CD34 was detected on vessels in all organs examined and was expressed during pancreatic and skin inflammatory episodes. A subset of HEV-like vessels in the inflamed pancreas of nonobese diabetic (NOD) mice are positive for both CD34 and GlyCAM 1, and bind to an L-selectin/immunoglobulin G (IgG) chimeric probe. Finally, we found that CD34 is present on vessels of deafferentiated PLN, despite the fact that these vessels are no longer able to interact with L-selectin or support lymphocyte binding in vitro or trafficking in vivo. Our data suggest that the regulation of posttranslational carbohydrate modifications of CD34 is critical in determining its capability to act as an L-selectin ligand. Based on its ubiquitous expression, we propose that an appropriately glycosylated form of vascular CD34 may act as a ligand for L-selectin-mediated leukocyte trafficking to both lymphoid and nonlymphoid sites.

Evaluating provider effectiveness

Purchaser and provider managers alike want to know that they are getting value for money; purchasers will require information about service effectiveness and cost effectiveness, and will increasingly monitor the extent to which provider planning strategies and management practices reflect the best use of this information. Catherine Kyle provides some guidelines for auditing effectiveness internally.

Serum fructosamine as a screening method for diabetes mellitus in patients with suspected acute myocardial infarction

It is important to identify diabetic patients in a coronary care population because they have a higher risk of suffering congestive heart failure, dysrhythmias and death following myocardial infarction. In order to determine the most efficient screening method for diabetes, we compared fructosamine and glucose measurements on admission blood specimens from 256 consecutive patients. Of 15 (5.9%) known diabetic patients, 12 had glucose results greater than or equal to 7.8 mmol/l and nine had fructosamine levels greater than 2.87 mmol/l. However, elevated glucose results were also found in a high proportion (49.2%) of patients with no previous history of diabetes. We performed glucose tolerance tests in 107 patients after discharge to determine the frequency of false-positive observations. Fructosamine yielded five (4.6%) false-positive results, whereas plasma glucose yielded 47 (43.9%) false-positive observations. We conclude that serum fructosamine provides a more specific screening method for diabetes in this population because the results are unaffected by stress hyperglycemia.