The effect of thyroid dysfunction on N-terminal pro-B-type natriuretic peptide concentrations

Background: B-type natriuretic peptides and N-terminal pro-B-type natriuretic peptides (NT-proBNP) have been suggested as being useful for the diagnosis of congestive heart failure. We have shown previously that changes in thyroid function are associated with changes in concentrations of other low molecular weight molecules. Therefore, the aim of this study was to assess whether similar changes occurred with NT-proBNP concentrations following treatment of thyroid dysfunction.

Methods: Seventeen patients (12 female, 5 male, age range 24-77 years) with newly diagnosed hypothyroidism and 21 patients (16 female, 5 male, age range 21-66 years) with newly diagnosed hyperthyroidism had NT-proBNP measured at baseline and when they subsequently became euthyroid.

Results: NT-proBNP levels were not significantly different in the hyperthyroid group from the hypothyroid, either before ( P = 0.706) or after treatment to euthyroidism ( P = 0.170). The hypothyroid group showed a rise in NT-proBNP after treatment ( P < 0.001). There was a marginally significant fall in the NT-proBNP levels in the hyperthyroid group ( P = 0.05). However, these changes were within the expected wide range of biological variability of NT-proBNP shown in earlier studies.

Conclusions: Hypothyroidism alters NT-proBNP concentrations, but the magnitude of this effect may be lost in the wide biological variability of natriuretic peptides and this statistically significant finding is not likely to be of clinical relevance.

Investigation into possible causes of interference in serum testosterone measurement in women

Background: Direct (non-extracted) testosterone immunoassays may give spuriously high results in women. The presumed interferents may be removed if testosterone is extracted into an organic phase before being measured. We aimed to clarify possible causes and effects of interference in testosterone measurement in women.

Methods: Women who had a blood sample referred to Hope Hospital Clinical Biochemistry laboratory for measurement of serum testosterone concentration over a six-month period were studied. Clinical and treatment data were recorded. A difference (direct-minus-extracted testosterone) of less than 1.0 nmol/L was used to define a group with low interference. A difference of 2.5 nmol/L or more was used to define a group with significant interference.

Results: The distribution of interference in 1271 serum samples from female patients was unimodal. There were no group differences in clinical presentation or treatment. The median degree of interference was 1.4 nmol/L. In 42 female patients with varying degrees of interference, identified on routine assay, regression analysis showed strong association between dehydroepiandrosterone sulphate (DHEA-S) and interference (direct-minus-extracted testosterone) ( r = 0.77, P<0.001).

Conclusions: Given that DHEA-S is present in very variable amounts in blood, it is possible that even with a low cross reactivity, DHEA-S or one of its metabolites significantly interferes in the testosterone assay when at higher concentrations.

The LH/FSH ratio has little use in diagnosing polycystic ovarian syndrome

Background: The luteinizing hormone/follicle stimulating hormone (LH/FSH) ratio is often requested to help diagnose polycystic ovarian syndrome (PCOS) despite a recent consensus recommending against its use. This study aimed to compare the variability of the LH/FSH ratio in PCOS with that of normal menstruating women over a full cycle in order to establish the diagnostic utility, or otherwise, of the test.

Methods: Twelve women with PCOS and 11 matched controls had blood collected at four-day intervals on 10 consecutive occasions over a complete menstrual cycle.

Results: The median LH/FSH ratio for individual subjects did not differ significantly between the PCOS and the non-affected group (1.6 versus 1.2, P=0.14). Only 7.6% of samples from PCOS patients had an LH/FSH ratio above three, compared with 15.6% of samples from normal subjects.

Conclusion: This study confirms that measurement of the LH/FSH ratio is of limited use in the diagnosis of PCOS.

Diabetes and chocolate: friend or foe?

Polyphenols and other compounds found in cocoa and chocolate have therapeutic potential in the management of diabetes in humans. Polyphenol benefits have been proposed supported by in vitro studies, animal work, and clinical trials, which have been conducted mostly in healthy volunteers. The energy-dense formulations of many cocoa and chocolate products, which can be up to 50% sugar by weight, have given the perception that chocolate may be harmful through its contribution to obesity. A review of both clinical trial databases and published literature yielded 15 registered trials and 7 published studies. The published data interventions reported are diverse and vary widely in quality, including poor selection of control products or inadequate blinding procedures. There are also inconsistencies in reporting of data with limited information on the effect of cocoa and chocolate supplementation on weight and glycemic control despite the potential benefits reported with respect to the cardiovascular risk factors of endothelial function and lipids. More studies are required powered for primary clinical outcomes together with the development of standardized product formulations that optimize the dose of polyphenols within a palatable and energy-restricted product.

The effect of anaemia and abnormalities of erythrocyte indices on HbA1c analysis: a systematic review

AIMS/HYPOTHESIS

The use of HbA1c for the diagnosis of diabetes is now widely advocated despite caveats to its use. Anaemia is cited as a major confounder to this use; however, the effect of erythrocyte indices and to what degree anaemia influences HbA1c levels is not known.

METHODS

A systematic electronic database search of MEDLINE, EMBASE, the Cumulative Index to Nursing & Allied Health Literature (CINAHL) and the Cochrane Library was conducted for relevant articles published between January 1990 and May 2014. Included studies had at least one measurement of HbA1c and glucose, and a least one index of haematinic deficiency, involving non-pregnant adults, not known to have diabetes.

RESULTS

A total of 12 articles from 544 were included. The majority of studies focused on iron deficiency anaemia (IDA) and, in general, demonstrated that the presence of iron deficiency with or without anaemia led to an increase in HbA1c values compared with controls, with no concomitant rise in glucose indices. Data on the effects of other indices of erythrocyte abnormalities on HbA1c are limited but show a possible decrease in HbA1c values with non-iron deficiency forms of anaemia.

CONCLUSIONS/INTERPRETATION

HbA1c is likely to be affected by iron deficiency and IDA with a spurious increase in HbA1c values; conversely, non-IDA may lead to a decreased HbA1c value. This may lead to confusion when diagnosing diabetes using HbA1c. This review clearly identifies the need for more evidence, especially in identifying the types and degrees of anaemia likely to have significant impact on the reliability of HbA1c.

The obesity paradox in type 2 diabetes mellitus: relationship of body mass index to prognosis: a cohort study

BACKGROUND

Whether obesity is associated with a better prognosis in patients with type 2 diabetes mellitus is controversial.

OBJECTIVE

To investigate the association between body weight and prognosis in a large cohort of patients with type 2 diabetes followed for a prolonged period.

DESIGN

Prospective cohort.

SETTING

National Health Service, England.

PATIENTS

Patients with diabetes.

MEASUREMENTS

The relationship between body mass index (BMI) and prognosis in patients with type 2 diabetes without known cardiovascular disease at baseline was investigated. Information on all-cause mortality and cardiovascular morbidity (such as the acute coronary syndrome, cerebrovascular accidents, and heart failure) was collected. Cox regression survival analysis, corrected for potential modifiers, including cardiovascular risk factors and comorbid conditions (such as cancer, chronic kidney disease, and lung disease), was done.

RESULTS

10,568 patients were followed for a median of 10.6 years (interquartile range, 7.8 to 13.4). Median age was 63 years (interquartile range, 55 to 71), and 54% of patients were men. Overweight or obese patients (BMI >25 kg/m²) had a higher rate of cardiac events (such as the acute coronary syndrome and heart failure) than those of normal weight (BMI, 18.5 to 24.9 kg/m²). However, being overweight (BMI, 25 to 29.9 kg/m²) was associated with a lower mortality risk, whereas obese patients (BMI >30 kg/m²) had a mortality risk similar to that of normal-weight persons. Patients with low body weight had the worst prognosis.

LIMITATION

Data about cause of death were not available.

CONCLUSION

In this cohort, patients with type 2 diabetes who were overweight or obese were more likely to be hospitalized for cardiovascular reasons. Being overweight was associated with a lower mortality risk, but being obese was not.

PRIMARY FUNDING SOURCE

National Institute for Health Research and University of Hull.

Haemoglobin A1c in the diagnosis and monitoring of diabetes mellitus

Haemoglobin A(1c) (HbA(1c)) is due to celebrate its 40th birthday. Many people would argue that the clinical studies relating the test to diabetes complications while in its late 20s are likely to be its finest ever achievement. However, this article looks at how HbA(1c) has matured since then and discusses in detail how its many strengths and idiosyncrasies as a marker of glycaemic risk have, as a 30-something, become more clearly understood. As HbA(1c) approaches middle age, this paper also describes how the test appears to be developing a mid-life crisis, as debate over how its results should be expressed seems likely to divide opinion among clinicians for some time to come.

The effects of treatment with liraglutide on atherothrombotic risk in obese young women with polycystic ovary syndrome and controls

BACKGROUND

Polycystic ovary syndrome (PCOS) is associated with obesity and increased cardiovascular (CV) risk markers. In this study our aim was to assess the effects of six months treatment with liraglutide 1.8 mg od on obesity, and CV risk markers, particularly platelet function, in young obese women with PCOS compared to controls of similar age and weight.

METHODS

Carotid intima-media wall thickness (cIMT) was measured by B-mode ultrasonography, platelet function by flow cytometry, clot structure/lysis by turbidimetric assays and endothelial function by ELISA and post-ischaemic reactive hyperemia (RHI). Data presented as mean change (6-month - baseline) ± standard deviation.

RESULTS

Nineteen obese women with PCOS and 17 controls, of similar age and weight, were recruited; baseline atherothrombotic risk markers did not differ between the two groups. Twenty five (69.4%) participants completed the study (13 PCOS, 12 controls). At six months, weight was significantly reduced by 3.0 ± 4.2 and 3.8 ± 3.4 kg in the PCOS and control groups, respectively; with no significant difference between the two groups, P = 0.56. Similarly, HOMA-IR, triglyceride, hsCRP, urinary isoprostanes, serum endothelial adhesion markers (sP-selectin, sICAM and sVCAM), and clot lysis area were equally significantly reduced in both groups compared to baseline. Basal platelet P-selectin expression was significantly reduced at six months in controls -0.17 ± 0.26 but not PCOS -0.12 ± 0.28; between groups difference, 95% confidence interval = -0.14 - 0.26, P = 0.41. No significant changes were noted in cIMT or RHI.

CONCLUSIONS

Six months treatment with liraglutide (1.8 mg od) equally affected young obese women with PCOS and controls. In both groups, liraglutide treatment was associated with 3-4% weight loss and significant reduction in atherothrombosis markers including inflammation, endothelial function and clotting. Our data support the use of liraglutide as weight loss medication in simple obesity and suggest a potential beneficial effect on platelet function and atherothrombotic risk at 6 months of treatment.

TRIAL REGISTRATION

Clinical trial reg. no. ISRCTN48560305. Date of registration 22/05/2012.

Current Evidence and Future Perspectives on the Effective Practice of Patient-Centered Laboratory Medicine

BACKGROUND

Systematic evidence of the contribution made by laboratory medicine to patient outcomes and the overall process of healthcare is difficult to find. An understanding of the value of laboratory medicine, how it can be determined, and the various factors that influence it is vital to ensuring that the service is provided and used optimally.

CONTENT

This review summarizes existing evidence supporting the impact of laboratory medicine in healthcare and indicates the gaps in our understanding. It also identifies deficiencies in current utilization, suggests potential solutions, and offers a vision of a future in which laboratory medicine is used optimally to support patient care.

SUMMARY

To maximize the value of laboratory medicine, work is required in 5 areas: (a) improved utilization of existing and new tests; (b) definition of new roles for laboratory professionals that are focused on optimizing patient outcomes by adding value at all points of the diagnostic brain-to-brain cycle; (c) development of standardized protocols for prospective patient-centered studies of biomarker clinical effectiveness or extraanalytical process effectiveness; (d) benchmarking of existing and new tests in specified situations with commonly accepted measures of effectiveness; (e) agreed definition and validation of effectiveness measures and use of checklists for articles submitted for publication. Progress in these areas is essential if we are to demonstrate and enhance the value of laboratory medicine and prevent valuable information being lost in meaningless data. This requires effective collaboration with clinicians, and a determination to accept patient outcome and patient experience as the primary measure of laboratory effectiveness.

LDL cholesterol variability in patients with Type 2 diabetes taking atorvastatin and simvastatin: a comparison of two formulae for LDL-C estimation

Background

A new formula was recently proposed by Cordovo et al. that was more highly correlated with low-density lipoprotein (LDL) measured directly than the Friedewald LDL formula. We conducted this prospective study to establish whether the new formula allows true variations in LDL within the same individual to be tracked more closely than that of the Friedewald formula.

Methods

A cross-over study of biological variation of lipids in 26 patients with Type 2 diabetes (T2DM) taking either a short half-life statin, simvastatin 40 mg ( n = 10), or a long half-life statin, atorvastatin 10 mg. After three months on one statin, fasting lipids were measured on 10 occasions over a five-week period. The same procedure was then followed for the other statin. The LDL was measured by a direct LDL immunoassay and was compared to the LDL estimated by the Friedewald and Cordova (0.7516) × (total cholesterol [TC]−high-density lipoprotein cholesterol [HDL-C]) formulae.

Results

As a group, the calculated or measured mean LDL was no different between statins. However, the biological coefficient of variation (CV) of directly measured LDL was far larger with simvastatin than atorvastatin. This difference was detected by Cordova LDL but not found with the Friedewald LDL formula.

Conclusions

In contrast to Friedewald LDL, Cordova LDL estimation revealed LDL to be much more stable in T2DM patients taking atorvastatin rather than simvastatin that was in accord with LDL when measured directly. Therefore, Cordova LDL which is a measure of non-HDL-cholesterol is the simplest, cheapest and the most convenient measurement for assessment of response to statin treatment.

Glucagon-like peptide-1 analogue, liraglutide, improves liver fibrosis markers in obese women with polycystic ovary syndrome and nonalcoholic fatty liver disease

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) has been linked to polycystic ovary syndrome (PCOS) and carries an increased risk of liver cirrhosis. Procollagen type 3 amino-terminal peptide (PIIINP) is an independent predictor of liver cirrhosis.

OBJECTIVE

To assess whether 6-month treatment with GLP-1 analogue, liraglutide, improves markers of liver fibrosis.

DESIGN

A case-control study comparing women with PCOS to age- and weight-matched controls. PCOS was diagnosed according to the Rotterdam criteria. All participants underwent liver function tests and liver ultrasound scan to assess for fatty infiltration. Serum marker for liver fibrosis, PIIINP, was measured at baseline and after 6-month treatment with liraglutide 1·8 mg od.

RESULTS

Nineteen women with PCOS and 17 controls were recruited, age 32·8 ± 7·2 vs 33·5 ± 6·7 years and weight 100·9 ± 16·7 vs 99·3 ± 14·7 kg, respectively. At baseline, the PCOS group had higher testosterone 1·2 ± 0·3 vs 0·9 ± 0·3 nm (P = 0·01), HOMA-IR 5·1 ± 2·6 vs 3·5 ± 1·3 (P = 0·03), AST 22·4 ± 5·2 vs 18·8 ± 3·4 u/l (P = 0·04), PIIINP 4·4 ± 0·8 vs 3·5 ± 0·8 ug/ml (P = 0·01) and NAFLD seven (35%) vs none (P = 0·005), respectively. Twenty-five (69%) participants completed the study (13 PCOS, 12 controls). Following treatment, weight was reduced by 3·0 ± 4·2 kg (P = 0·01) and 3·8 ± 3·4 kg (P = 0·001), respectively. Similarly, HOMA-IR, hsCRP, triglycerides and urinary isoprostane significantly reduced in both groups. PIIINP significantly reduced the in PCOS group 4·4 ± 0·8 vs 3·7 ± 0·9 ug/ml (P < 0·01), but not in controls 3·5 ± 0·8 vs 3·2 ± 0·7 ug/ml (P = 0·08).

CONCLUSIONS

Treatment with liraglutide, and/or associated weight loss, significantly reduced PIIINP levels in obese women with PCOS. This may be an additional beneficial factor when considering the use of liraglutide in women with PCOS, obesity and NAFLD.

A comparison of cardiovascular risk indices in patients with polycystic ovary syndrome with and without coexisting nonalcoholic fatty liver disease

BACKGROUND

Women with polycystic ovary syndrome (PCOS) have an adverse cardiovascular risk profile and an increased prevalence of nonalcoholic fatty liver disease (NAFLD), which is also associated with an adverse cardiovascular risk profile.

OBJECTIVE

To compare the cardiovascular risk profile of women with PCOS alone and women with PCOS and NAFLD.

DESIGN, SETTING AND PARTICIPANTS

Twenty-five oligoanovulatory women with PCOS were screened for NAFLD (including liver biopsy if appropriate) and had their cardiovascular risk factors measured which included the inflammatory marker C-reactive protein (CRP), endothelial function {measured using endoPAT 2000 and serum markers [intracellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin and P-selectin]}, clot structure and function [maximum absorbance (MA) and lysis potential (LT)].

RESULTS

Twelve patients had confirmed PCOS without evidence of NAFLD, and 13 patients had confirmed PCOS with evidence of NAFLD. The PCOS and NAFLD group were heavier (BMI 43·9 ± 2·2 kg/m(2) ) compared with the PCOS alone group (BMI 37·6 ± 1·4 kg/m(2) P = 0·03). There was no difference in CRP (7·57 ± 0·95 vs 6·59 ± 1·87 mm P = 0·62) or endothelial function (RH-PAT 1·96 ± 0·1 vs 1·74 ± 0·16 P = 0·25), ICAM-1 (221 ± 48 vs 250 ± 60 ng/ml P = 0·19), VCAM-1 (2124 ± 78 vs 2314 ± 91 ng/ml P = 0·13), E-selectin (33·9 ± 3·3 vs 39·5 ± 15·5 ng/ml P = 0·31) and P-selectin (101·0 ± 6·6 vs 95·9 ± 10·2 ng/ml P = 0·69). There was no difference in clot formation or lysis.

CONCLUSION

The patients with PCOS and NAFLD were heavier compared with patients with PCOS alone. Despite this, we were unable to demonstrate differences in inflammatory markers, endothelial function or clot structure and function, suggesting that severity of steatosis is not the most important determinant of cardiovascular risk in PCOS.

Postprandial effects of long-term niacin/laropiprant use on glucose and lipid metabolism and on cardiovascular risk in patients with polycystic ovary syndrome

AIM

This study investigated the effect of long-term niacin/laropiprant therapy on CV risk and IR in obese women with PCOS.

METHODS

In this double-blind randomized placebo-controlled trial, 13 and 12 PCOS women completed a 12 week course of niacin/laropiprant or placebo, respectively. Fasted subjects had an endothelial function test (EndoPat2000) and then consumed a mixed meal with blood sampled postprandially for 6 h before and after intervention.

RESULTS

By 12 weeks, niacin/laropiprant lowered low-density lipoprotein cholesterol (LDL-c) (13%) and increased HDL-c (17%). Despite a reduction in fasting triglycerides (21%), the drug had no effect on their postprandial rise (2.69 ± 1.44 vs. 2.49 ± 1.14 mmol/l, p = 0.72). However, following the mixed meal, plasma glucose area under the response curve increased from 13.1 ± 2.9 to 14.0 ± 2.8 mmol/l, p = 0.05, as a consequence of both increased insulin resistance [HOMA-IR: 2.2 (1.2, 4.2) vs. 3.8(1.3, 5.5), p = 0.02] and a reduced acute insulin response to glucose [424 (211, 975) vs. 257(122, 418) pmol/mmol, p = 0.04]. Niacin/laropiprant did not improve RHI (1.97 ± 0.40 vs. 2.05 ± 0.58, p = 0.33) or hsCRP.

CONCLUSIONS

In PCOS, niacin/laropiprant had a significant negative impact on postprandial glucose and no improvement in postprandial hypertriglyceridaemia, with at least the former mediated through increased IR and reduced β-cell function. This data may help explain why the improvement in fasting lipids has not translated into improved CV risk markers in PCOS.

Acute hypertriglyceridemia induces platelet hyperactivity that is not attenuated by insulin in polycystic ovary syndrome

Background

Atherothrombosis is associated with platelet hyperactivity. Hypertriglyceridemia and insulin resistance (IR) are features of polycystic ovary syndrome (PCOS). The effect of induced hypertriglyceridemia on IR and platelet function was examined in young women with PCOS.

Methods and Results

Following overnight fasting, 13 PCOS and 12 healthy women were infused with saline or 20% intralipid for 5 hours on separate days. Insulin sensitivity was measured using a hyperinsulinemic euglycaemic clamp in the final 2 hours of each infusion. Platelet responses to adenosine diphosphate (ADP) and prostacyclin (PGI₂) were measured by flow cytometric analysis of platelet fibrinogen binding and P‐selectin expression using whole blood taken during each infusion (at 2 hours) and at the end of each clamp. Lipid infusion increased triglycerides and reduced insulin sensitivity in both controls (median, interquartile range ) (5.25 [3.3, 6.48] versus 2.60 [0.88, 3.88] mg kg⁻¹ min⁻¹, P<0.001) and PCOS (3.15 [2.94, 3.85] versus 1.06 [0.72, 1.43] mg kg⁻¹ min⁻¹, P<0.001). Platelet activation by ADP was enhanced and ability to suppress platelet activation by PGI₂ diminished during lipid infusion in both groups when compared to saline. Importantly, insulin infusion decreased lipid‐induced platelet hyperactivity by decreasing their response to 1 μmol/L ADP (78.7% [67.9, 82.3] versus 62.8% [51.8, 73.3], P=0.02) and increasing sensitivity to 0.01 μmol/L PGI₂ (67.6% [39.5, 83.8] versus 40.9% [23.8, 60.9], P=0.01) in controls, but not in PCOS.

Conclusion

Acute hypertriglyceridemia induced IR, and increased platelet activation in both groups that was not reversed by insulin in PCOS subjects compared to controls. This suggests that platelet hyperactivity induced by acute hypertriglyceridemia and IR could contribute athero‐thrombotic risk.

Clinical Trial Registration

URL: www.isrctn.org. Unique Identifier: ISRCTN42448814.

Glycemic Control in the 12 Months following a Change to SI Hemoglobin A1c Reporting Units

BACKGROUND

Many countries have implemented, or are considering, a change in hemoglobin A1c (Hb A1c) units from traditional percentage values [Diabetes Control and Complications Trial (DCCT)] to the new Système International d'Unités (SI) unit in millimoles per mole. Concern exists that such a large alteration in numeric values might lead, through confusion, to a deterioration in patients' glycemia. This study has assessed Hb A1c in the year before and after the change of units in a UK diabetes population.

METHODS

The Hb A1c in the 12 months immediately before the unit change (October 2010 to September 2011) was compared with the 12 months after (October 2011 to September 2012). Also, the subsequent change in Hb A1c in patients who had poor glycemic control [Hb A1c &gt;8% (64 mmol/mol)], either before or after the unit change, was compared.

RESULTS

Over the 2 years, 44 721 Hb A1c measurements were requested on 13 197 (7247 male, 5950 female) known diabetes patients. The population Hb A1c was no different between years, with a median [interquartile range (IQR)] value of 7.5% (6.6%–8.7%) after the change and 7.5% (6.5–8.7) before (P = 0.34). The subsequent change in Hb A1c following a raised (&gt;8%) result was the same regardless of whether the initial value reported was in DCCT or SI units [median (IQR) change in Hb A1c −0.2% (−0.9% to 0.3%), n = 4316, following a DCCT result, vs −0.2% (−0.8% to 0.3%), n = 4396, following SI; P = 0.44].

CONCLUSIONS

In this UK diabetes population, a move to SI Hb A1c reporting did not lead to any marked short-term deterioration in glycemia or a different Hb A1c outcome in patients with initial poor glucose control.

Use of complementary markers in assessing glycaemic control in people with diabetic kidney disease undergoing iron or erythropoietin treatment

AIMS

HbA(1c) values are unreliable in patients with diabetes who have chronic kidney disease who receive iron and/or erythropoiesis stimulating agents. The study aimed to evaluate the utility of the complementary glycaemic markers glycated albumin, fructosamine and 1,5 anhydroglucitol in this group of patients.

METHODS

A prospective study of patients with Type 2 diabetes and chronic kidney disease stage IIIB/IV undergoing intravenous iron or erythropoiesis-stimulating agent therapy. Glycaemic control was monitored using HbA(1c), seven-point daily glucose thrice weekly, continuous glucose monitoring, glycated albumin, fructosamine and 1,5 anhydroglucitol.

RESULTS

Fifteen patients [9 men; median age 72 years (interquartile range 68-74), follow-up period (16.4 ± 3.7 weeks)] received parenteral iron; 15 patients [11 men; 70 years (interquartile range 62-75), (17.3 ± 3.3 weeks)] received erythropoiesis-stimulating agent. HbA(1c) fell following treatment with both iron [57 mmol/mol (7.4%) to 53 mmol/mol (7.0%), P < 0.001] and erythropoiesis-stimulating agent [56 mmol/mol (7.3%) to 49 mmol/mol (6.6%), P = 0.01] despite mean blood glucose remaining unchanged (iron: 9.55 to 9.71 mmol/l, P = 0.07; erythropoiesis-stimulating agent: 8.72 to 8.78 mmol/l, P = 0.89). Unlike HbA1c , the glycated albumin, fructosamine and 1,5 anhydroglucitol levels did not change following iron [glycated albumin (16.8 to 16.3%, P = 0.10); fructosamine (259.5 to 256 μmol/l, P = 0.89); 1,5 anhydroglucitol (54.2 to 50.9 μmol/l, P = 0.89)] or erythropoiesis-stimulating agent [glycated albumin (17.9 to 17.5%, P = 0.29), fructosamine (324.3 to 306.0 μmol/l, P = 0.52), 1,5 anhydroglucitol (58.2 to 46.7 μmol/l, P = 0.35)]. Despite this, HbA(1c) was consistently the marker most closely related to mean blood glucose before and after each treatment (R range 0.7-0.88).

CONCLUSIONS

These data indicate that HbA(1c) was statistically most closely related to mean blood glucose, but clinical trends in glycaemia in patients undergoing iron or erythropoiesis-stimulating agent therapy are likely best assessed by including one of these additional glycaemic markers.

Biological variation of cardiovascular risk factors in patients with diabetes

Biological variation refers to the natural fluctuations found when repeated measurements are made in a biological system. Generally, biological variation remains within narrow boundaries in health, but may differ in pathological states, with implications for the diagnosis and monitoring of disease processes. In disease, biological variation may alter such that any subsequent measurement may need to have a greater difference compared with a healthy control to be biologically relevant. Treatments such as insulin or anti-hypertensive therapy have been shown to reduce biological variability closer to normal levels and theoretically this may help prevent complication development or progression in conditions such as diabetes. This article reviews how biological variation can influence our identification and assessment of vascular risk factors in a person with diabetes. The role of biological variation in the diagnosis of diabetes (glucose and HbA1c) is then examined. Finally, the influence that common treatments in diabetes have in modifying biological variation is described.