Evaluation of the MP Rapid 2019-NCOV IgM/IgG combo POCT test vs. an established platform-based method

BACKGROUND

Accurate and rapid testing for SARS-COV-2 antibodies could improve the diagnosis and management of COVID-19. In this study, we aim to evaluate the diagnostic accuracy of a commercially available point-of-care lateral flow kit independently and in comparison to an established platform-based system.

METHOD

Samples from 144 PCR-confirmed COVID-19 cases and 130 pre-pandemic negative controls were tested in parallel by MP Rapid 2019-NCOV IgM/IgG Combo test and Roche Elecsys. Comparison of results based on serum and capillary blood testing was undertaken.

RESULTS

Sensitivity at day 15 onwards was 100% for both methods. Between days 1 and 7 post admission, the IgM/IgG Combo test and Roche Elecsys shown sensitivity of 74% (95%CI: 62%-85%) vs. 67% (95% CI: 55%-79%, P = 0.3947). Combo test specificities were 100% for IgG, 98.5% for IgM vs. Roche Elecsys specificity of 100%. Concordance analysis showed 98.5% agreement to the Roche Elecsys method (Cohen's Kappa 0.96 95% CI [0.92-0.99]). Capillary blood results showed complete agreement with serum samples using the Combo test.

CONCLUSION

In comparison to Roche Elecsys, our data show that the MP Rapid 2019-NCOV IgM/IgG Combo test provides a high-confidence assay system for the detection of previous exposure to SARS-COV-2 infection with advantage of affording near-patient testing.

Albumin and calcium reference interval using healthy individuals and a data-mining approach

BACKGROUND

Harmonization of reference intervals for analytes that have a sound calibration and metrological traceability is a widely recommended practice. The UK Pathology Harmony has recently harmonized reference intervals for calcium and albumin. In this study, we have determined the reference intervals for calcium and albumin on the UK's most commonly used analytical platforms.

METHOD

A prospective reference population of healthy individuals was recruited according to the IFCC CRIDL criteria. A second indirect population was collected from 14 primary care setting and measured in laboratories using various analytical platforms and methods (Roche, Abbott, Beckman and Siemens analytical platforms).

RESULTS

In total, 299 subjects were recruited; the central 95th centile values for calcium for three out of four analytical platforms were in a close agreement with UK Pathology Harmony reference intervals of 2.2-2.6 mmol/L. Reference intervals of BCG methods from both cohorts and irrespective of analytical platforms were higher for both lower and upper reference limits than those for BCP. In comparison, the indirect study showed an age-related variation. The younger population reference intervals varied by up to 5.7% at the lower reference limit and up to 12% at the upper reference limit compared with Pathology Harmony reference intervals, and the older population showed a variation of up to 14% at both limits.

CONCLUSION

While calcium reference intervals can be a subject for harmonization, albumin reference intervals studied showed large variation which is unsupportive of embracing a common reference interval for albumin.

The impact of the analytical performance specifications of calcium and albumin on adjusted calcium

Aim

The generation of accurate, comparable results from traceable measurement procedures is a primary goal in harmonization efforts. In this study, the analytical performance of routine methods for calcium and albumin measurement is assessed to define the impact of the analytical bias of calcium and albumin on adjusted calcium equation performance and on reference intervals.

Method

In collaboration with the Wales External Quality Assurance Scheme, six months’ worth of anonymized data that cover a concentration range of clinical interest were collected. The data were grouped by analytical platforms/methods.

Results

Albumin BCG methods are positively biased (8%) to BCP methods. The overall bias for BCP methods ranges from 5.1 to –4.3% and the overall bias for BCG methods is from 2 to –6.7%. Bias for both methods is higher than the allowable minimal bias for albumin. Calcium concentrations for Roche Cobas CPC and NM-BAPTA, Beckman Arsenazo III, Abbott Architect Arsenazo III were within bias of 1.5 to –1%. However, Siemens calcium methods CPC and Arsenazo III appear to suffer from concentration-dependent bias ranging from +3 to –6%, which exceeds even the minimal allowable limits for calcium (1.3%). Adjusted calcium shows significant bias of 11%. Even with the exclusion of Siemens Advia, the scatter of adjusted calcium results exceeds that for total calcium.

Conclusion

This study shows wider than acceptable analytical variation for albumin and calcium. This variation may contribute to overall adjusted calcium equations variation and invalidate the application of a harmonized reference interval for calcium and albumin.

The effect of different analytical platforms and methods on the performance of population-specific adjusted calcium equation

Background

A recent attempt to improve the diagnostic value of adjusted calcium addressed a primary care-specific adjusted calcium equation, but validated the new equation for Roche Cobas, BCG and NM-BAPTA methods only. In this study, we aim to validate a population-specific equation for other methods and platforms.

Method

We collected retrospective patient data-sets from 15 hospital laboratories using a range of commercially available analytical platforms and methods for calcium and albumin measurements. Raw data-sets were collected and filtered according to Payne’s criteria, and separate adjusted calcium equations were derived for hospitalized and primary care patients.

Results

Mean albumin and calcium results were significantly higher in primary care populations ( P <  0.0001). The prevalence of hypocalcaemia using adjusted calcium ranged between 6% and 44% for inpatient data-sets and was higher in users of BCG methods. The application of community-specific adjustment equation to primary care data-sets reduced the prevalence of hypocalcaemia (mean 1.7%, range 0.8–3.7%).

Conclusion

We demonstrated that the use of a community-specific calcium adjustment equation to a primary care population reduces both the percentage and the variation of hypocalcaemia between different laboratories.

Prospective study comparing the outcome of a population-specific adjusted calcium equation to ionized calcium

Background

Calcium circulates bound to albumin and changes in albumin concentration will therefore affect total calcium measurements. In order to mitigate this, correction factors are frequently used. The most widely used correction equation was described by Payne and colleagues in 1973. This equation was derived from well-defined hospitalized patients’ data. Current clinical practice is consistent with the general application of the adjusted calcium equation irrespective of clinical setting. This study aims to assess the validity of this approach by the derivation of a community care-specific adjusted calcium equation (‘community equation’) and the comparison of its performance to a hospitalized patient equation and ionized calcium.

Method

Retrospective data were collected according to Payne’s criteria from an inpatient and community care setting. Data were used to derive the two equations: the in-patient equation and community equation. The outcome of these equations was compared with ionized calcium obtained from 123 healthy participants.

Results

The community equation correctly identified the calcium status of 92% of the 123 healthy participants, while the inpatient equation identified 46% only. Regression analysis against ionized calcium showed a higher R2 for the community equation than for the inpatient equation. Furthermore, we have shown that mean albumin and calcium concentrations are significantly different between these two populations.

Conclusion

In this study, we found that the diagnostic accuracy of the adjusted calcium equation in ambulant patients was improved by the derivation of a population-specific equation for the community care setting.

High-dose oral colecalciferol loading in obesity: impact of body mass index and its utility prior to bariatric surgery to treat vitamin D deficiency

Obesity is associated with lower vitamin D levels compared with normal weight subjects, and if levels are not replaced prior to bariatric surgery, this can increase fracture risk as bone density typically falls post-operatively. We analysed the effect of body mass index (BMI) on vitamin D levels in response to 300 000 IU of colecalciferol in patients with vitamin D deficiency (<30 nmol L^-1 ). Patients were grouped according to their BMI as normal weight (20-24.9 kg m^-2 ), overweight (25-29.9 kg m^-2 ), obese class I (30-34.9 kg m^-2 ) and obese class II and above (>35 kg m^-2 ). The records were retrospectively analysed to investigate the effects of BMI on vitamin D (total 25-hydroxy vitamin D [25(OH)D]), serum Ca²⁺ and parathyroid hormone (PTH) levels at 6, 12, 26 and 52 weeks compared with baseline. Compared with normal weight subjects, overweight and obese patients achieved lower mean peak total 25(OH)D levels (6 weeks post-loading), which was most significant in the class II and above group (mean total 25(OH)D levels 96.5 ± 24.2 nmol L^-1 and 72.42 ± 24.9 nmol L^-1 , respectively; P = 0.003). By 26 weeks, total 25(OH)D levels fell in all groups; however, there was now a significant difference between the normal weight subjects and all other groups (mean total 25(OH)D levels 84.1 ± 23.7 nmol L^-1 ; 58 ± 20 nmol L^-1 , P = 0.0002; 62.65 ± 19.2 nmol L^-1 , P = 0.005; 59.2 ± 21 nmol L^-1 , P = 0.005, respectively). Far fewer patients in the overweight and obese groups maintained levels above the recommended level of 75 nmol L^-1 52 weeks post-loading (93%; 20%, P = 0.0003; 23%, P = 0.01; and 14%, P = 0.001, respectively). Alternative regimes for the treatment of vitamin D deficiency are needed in overweight and obese patients, especially those in whom bariatric surgery is planned.

Anti-Müllerian hormone reflects the severity of polycystic ovary syndrome

OBJECTIVE

To examine the relationship between anti-Müllerian hormone (AMH) and the severity of the phenotype of patients with polycystic ovary syndrome (PCOS) and whether AMH can act as a diagnostic marker for PCOS?

DESIGN

A prospective diagnostic utility study of AMH as a marker of PCOS.

PATIENTS

A consecutive series of women presenting to a tertiary infertility clinic (n = 164) plus a second series of women prepared for assisted conception treatments (n = 89) recruited between June 2012 and May 2013.

MEASUREMENTS

Polycystic ovary syndrome was diagnosed using the Rotterdam criteria. AMH was measured using the Generation II assay (Beckman Coulter). The diagnostic utility of AMH was established using receiver operator characteristic (ROC) curves. Cut-off values for the individual features of PCOS are proposed.

RESULTS

There was a significant difference in serum AMH concentration in women with normal ovaries (13·2 pmol/l), polycystic ovary morphology (PCOM) alone (37·8 pmol/l) and PCOS (53·2 pmol/l). Follicle number, increasing cycle length and evidence of hyperandrogenism were all independently associated with serum AMH concentration (P < 0·01). AMH was significantly affected by the different phenotypic presentations of PCOS with those with all components (PCOM, HA and OA) having the highest mean value [72·7 pmol/l (P < 0·01)].

CONCLUSIONS

Serum AMH has the capacity to act as a diagnostic test for PCOS. Moreover, since its value rises with the more marked phenotypes, different cut-off values need to be used to differentiate those patients with polycystic ovarian morphology (PCOM), hyperandrogenism (HA) and oligoanovulation (OA).

A short course of metformin does not reduce OHSS in a GnRH antagonist cycle for women with PCOS undergoing IVF: a randomised placebo-controlled trial

STUDY QUESTION

Does 'metformin' reduce the incidence of ovarian hyperstimulation syndrome (OHSS) for women with polycystic ovary syndrome (PCOS) undergoing a GnRH antagonist assisted conception treatment cycle?

SUMMARY ANSWER

A short course of metformin does not reduce the incidence of OHSS for women with PCOS undergoing a GnRH antagonist treatment cycle.

WHAT IS KNOWN ALREADY

Metformin does reduce the incidence of OHSS in a GnRH-agonist treatment cycle.

STUDY DESIGN, SIZE, DURATION

A randomised placebo-controlled trial (RCT) using metformin or placebo. Randomisation was blinded to both patient and investigator, using a random permuted blocks method with a 50:50 allocation ratio. The study was completed over 5 years (2009-2014) with 153 randomised patients. A sample size calculation based on the incidence of OHSS was completed prospectively suggesting a minimum of 146 recruits was required for the trial with a power of 80% and a type 1 error of 0.05.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All patients met the Rotterdam criteria for PCOS and were treated with a standard GnRH antagonist IVF/ICSI treatment cycle in a tertiary infertility clinic. The study medication was started prior to stimulation and continued to oocyte retrieval. Of the 153 patients, 77 received metformin and 76 placebo.

MAIN RESULTS AND THE ROLE OF CHANCE

There was no reduction in the incidence of moderate-severe OHSS (Placebo (PLA) 12.2%, metformin (MET) = 16%, 95% CI -0.08-0.16, P = 0.66). There was no difference in total gonadotrophin dose (PLA = 1200, MET = 1200, 95% CI -118.67-118.67, P = 0.75), oocytes retrieved (PLA = 15, MET = 14, 95% CI -2.37-4.37, P = 0.66) or fertilisation rate (PLA = 60.7%, MET = 53.3%, 95% CI -0.96-14.94, P = 0.07). However, using metformin resulted in a reduced clinical pregnancy rate (CPR) per cycle started (PLA = 48.7%, MET = 28.6%, 95% CI 0.04-0.35, P = 0.02) and live birth rate (PLA = 51.6%, MET = 27.6%, 95% CI 0.05-0.40, P = 0.02). Furthermore, when ethnicity was taken into account there was a significant reduction in pregnancy outcome for the South Asian population irrespective of metformin or placebo use (CPR per cycle started, White Caucasian = 44.4%, South Asian = 19.4%; 95% CI 0.06-0.39, P = 0.01).

LIMITATIONS, REASONS FOR CAUTION

This study was only undertaken on an infertility population with PCOS with a limited duration of study medication use.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first adequately powered RCT to assess the impact of metformin on OHSS in a high-risk group (women with PCOS) undergoing a GnRH antagonist cycle. It does not support the empirical prescribing of metformin as an adjunct to a GnRH antagonist treatment cycle.

STUDY FUNDING/COMPETING INTERESTS

None.

TRIAL REGISTRATION NUMBER

EudraCT number 2009-010952-81.

TRIAL REGISTRATION DATE

21 September 2009.

DATE OF FIRST PATIENT'S ENROLMENT

30 October 2009.

British Cardiac Society Working Group on the definition of myocardial infarction

The British Cardiac Society commissioned this report to help address inconsistencies in the terminology for acute coronary syndromes and wide variations in the threshold for the diagnosis of myocardial infarction (MI) depending on the assay performed, the precision, and the sensitivity. In addition, several publications have highlighted potential problems with the application of the European Society of Cardiology (ESC)/ American College of Cardiology (ACC) consensus document published in 2000. A revision process has been initiated under the guidance of the ESC, the ACC, and the American Heart Association (AHA). The purpose of this report is to help inform the next revision of the ESC/ACC/AHA guidelines for the diagnosis of MI.

The case of stainless statins

Two cases of hypercholesterolaemic patients are presented in whom raised plasma creatine kinase was noted during treatment with statins. The plasma creatine kinase failed to fall following cessation of therapy. Further investigation revealed the aetiology of the raised plasma creatine kinase to be due to previously undiagnosed glycogen storage diseases (McArdle's and Pompe's diseases).

The effect of metformin treatment in vivo on acute and long-term energy metabolism and progesterone production in vitro by granulosa cells from women with polycystic ovary syndrome

STUDY QUESTION

What are the consequences of polycystic ovary syndrome (PCOS) pathology and metformin-pretreatment in vivo in women with PCOS on the metabolism and steroid production of follicular phenotype- and long-term cultured-granulosa cells (GC)?

SUMMARY ANSWER

PCOS pathology significantly compromised glucose metabolism and the progesterone synthetic capacity of follicular- and long-term cultured-GCs and the metabolic impact of PCOS on GC function was alleviated by metformin-pretreatment in vivo.

WHAT IS KNOWN ALREADY

Granulosa cells from women with PCOS have been shown to have an impaired insulin-stimulated glucose uptake and lactate production in vitro. However, these results were obtained by placing GCs in unphysiological conditions in culture medium containing high glucose and insulin concentrations. Moreover, existing data on insulin-responsive steroid production in vitro by PCOS GCs vary.

STUDY DESIGN, SIZE AND DURATION

Case-control experimental research comparing glucose uptake, pyruvate and lactate production and progesterone production in vitro by GCs from three aetiological groups, all undergoing IVF; healthy control women (Control, n = 12), women with PCOS treated with metformin in vivo (Metformin, n = 8) and women with PCOS not exposed to metformin (PCOS, n = 8). The study was conducted over a period of 3 years between 2007 and 2010.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Rotterdam criteria were used for the diagnosis of PCOS; all subjects were matched for age, BMI and baseline FSH. Individual patient cultures were undertaken with cells incubated in a validated, physiological, serum-free culture medium containing doses of 0–6 mM glucose and 0–100 ng/ml insulin for 6 h and 144 h to quantify the impact of treatments on acute and long-term metabolism, respectively, and progesterone production. The metabolite content of spent media was measured using spectrophotometric plate reader assay. The progesterone content of spent media was measured by enzyme-linked immunosorbent assay. Viable GC number was quantified after 144 h of culture by the vital dye Neutral Red uptake assay.

MAIN RESULTS AND THE ROLE OF CHANCE

Granulosa cells from women with PCOS pathology revealed reduced pyruvate production and preferential lactate production in addition to their reduced glucose uptake during cultures (P < 0.05). Metformin pretreatment alleviated this metabolic lesion (P < 0.05) and enhanced cell proliferation in vitro (P < 0.05), but cells retained a significantly reduced capacity for progesterone synthesis compared with controls (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

Although significant treatment effects were detected in this small cohort, further studies are required to underpin the molecular mechanisms of the effect of metformin on GCs.

WIDER IMPLICATIONS OF THE FINDINGS

The individual patient culture strategy combined with multifactorial experimental design strengthens the biological interpretation of the data. Collectively, these results support the notion that there is an inherent impairment in progesterone biosynthetic capacity of the GCs from women with PCOS. The positive, acute metabolic effect and the negative long-term steroidogenic effect on GCs following metformin exposure in vivo may have important implications for follicular development and luteinized GC function when the drug is used in clinical practice.

STUDY FUNDING/COMPETING INTEREST(S)

No competing interests. This work was supported by the UK Medical Research Council Grant Reference number G0800250.

Cardiovascular risk in patients with small and medium abdominal aortic aneurysms, and no history of cardiovascular disease

Background

Cardiovascular disease (CVD) is the main cause of death in people with abdominal aortic aneurysm (AAA). There is little evidence that screening for AAA reduces all-cause or cardiovascular mortality. The aim of the study was to assess whether subjects with a small or medium AAA (3·0–5·4 cm), without previous history of clinical CVD, had raised levels of CVD biomarkers or increased total mortality.

Methods

This prospective study included subjects with a small or medium AAA and controls, all without a history of clinical CVD. CVD biomarkers (high-sensitivity C-reactive protein, hs-CRP; heart-type fatty acid-binding protein, H-FABP) were measured, and survival was recorded.

Results

Of a total of 815 people, 476 with an AAA and 339 controls, a cohort of 86 with small or medium AAA (3–5·4 cm) and 158 controls, all with no clinical history of CVD, were identified. The groups were matched for age and sex. The AAA group had higher median (i.q.r.) levels of hs-CRP (2·8 (1·2–6·0) versus 1·3 (0·5–3·5) mg/l; P &lt; 0·001) and H-FABP (4·6 (3·5–6·0) versus 4·0 (3·3–5·1) µg/l; P = 0·011) than controls. Smoking was more common in the AAA group; however, hs-CRP and H-FABP levels were not related to smoking. Mean survival was lower in the AAA group: 6·3 (95 per cent confidence interval (c·i.) 5·6 to 6·9) years versus 8·0 (7·6 to 8·1) years in controls (P &lt; 0·001). Adjusted mortality was higher in the AAA group (hazard ratio 3·41, 95 per cent c·i. 2·11 to 9·19; P &lt; 0·001).

Conclusion

People with small or medium AAA and no clinical symptoms of CVD have higher levels of hs-CRP and H-FABP, and higher mortality compared with controls. They should continue to receive secondary prevention against CVD.

The metabolic inter-relationships between changes in waist circumference, triglycerides, insulin sensitivity and small, dense low-density lipoprotein particles with acute weight loss in clinically obese children and adolescents

OBJECTIVE

Small, dense low-density lipoprotein (LDL) particles are highly atherogenic and strongly associated with obesity-related dyslipidemia. The metabolic inter-relationships between weight loss induced changes in waist circumference, triglycerides, insulin sensitivity and small-dense LDL particles in clinically obese children and adolescents have not been studied.

METHODS

Seventy-five clinically obese boys and girls (standardized body mass index 3.07 ± 0.59, aged 8-18 years) were recruited. Anthropometric, body composition and cardiometabolic risk factors were measured pre- and post-weight loss.

RESULTS

There were highly significant reductions in anthropometric, body composition and cardiometabolic risk factors. Triglyceride change was positively correlated with LDL peak particle density and percentage LDL pattern B changes (relative abundance of small, dense LDL particles). Multiple regression analyses showed that changes in triglyceride concentration accounted for between 24 and 18% of the variance in LDL peak particle density and percentage LDL pattern B change, respectively. Changes in waist circumference and insulin sensitivity did not predict these changes in LDL characteristics.

CONCLUSION

Acute and highly significant weight loss significantly decreased LDL peak particle density and percentage LDL pattern B. The change in triglycerides was a strong predictor of LDL peak particle density and percentage LDL pattern B change.

Analytical and clinical challenges in a patient with concurrent type 1 diabetes, subcutaneous insulin resistance and insulin autoimmune syndrome

A lean 15-year-old girl was diagnosed with type 1 diabetes based on symptomatic hyperglycaemia and positive anti-islet cell antibodies. Glycaemia was initially stabilised on twice-daily mixed insulin. After 11 months from the time of diagnosis, she complained of hyperglycaemia and ketosis alternating with hypoglycaemia. This progressively worsened until prolonged hospital admission was required for treatment of refractory hypoglycaemia. A high titre of anti-insulin antibodies was detected associated with a very low recovery of immunoreactive (free) insulin from plasma after precipitation with polyethylene glycol, suggesting the presence of insulin in bound complexes. Insulin autoimmune syndrome was diagnosed and metabolic fluctuations were initially managed supportively. However, due to poor glucose control, immunosuppressive therapy was initiated first with steroids and plasmapheresis and later with anti-CD20 antibody therapy (Rituximab). This treatment was associated with a gradual disappearance of anti-insulin antibodies and her underlying type 1 diabetes has subsequently been successfully managed with an insulin pump.

LEARNING POINTS

Anti-insulin antibodies may result in low levels of free insulin.Polyclonal anti-insulin antibodies can interfere with the pharmacological action of administered insulin, resulting in hypoglycaemia and insulin resistance, due to varying affinities and capacities.In this patient, rituximab administration was associated with a gradual disappearance of anti-insulin antibodies.It is hypothesised that this patient had subcutaneous insulin resistance (SIR) caused by insulin capture at the tissue level, either by antibodies or by sequestration.A prolonged tissue resistance protocol may be more appropriate in patients with immune-mediated SIR syndrome.

The effect of serum matrix and gender on cortisol measurement by commonly used immunoassays

Background

Considerable intermethod bias has been observed between cortisol immunoassays, with some also displaying a gender difference. Cortisol immunoassay performance is affected by serum matrix effects such as changes in steroid binding proteins and presence of interfering steroids which can be altered in various clinical settings. This study investigates cortisol immunoassay bias in pregnancy, renal failure and intensive care patients.

Methods

Serum remaining after routine analysis from pregnant patients, patients on the intensive care unit and patients with renal failure were obtained prior to disposal and used to create 20 anonymous samples per group. A male and female serum pool was prepared and spiked with cortisol. Samples were aliquoted and distributed to four hospitals for cortisol analysis by immunoassays from four different manufacturers. Cortisol was also measured by an isotope dilution-gas chromatography–mass spectrometry method for comparison of assay bias.

Results

Differences in cortisol immunoassay bias were observed across the different patient groups. A negative bias compared to pooled serum samples was observed for pregnancy serum, whilst a more positive bias was seen in renal failure and intensive care patients. Variation in bias was greatest in renal failure with the Roche E170 the most affected and the Abbott architect the least (interquartile ranges 44% and 14%, respectively).

Conclusions

Cortisol immunoassay bias may be affected by gender and differences in serum matrix from patients with various clinical conditions. Users of cortisol assays should be aware of differing matrix effects on their assay and the relevance of these for the interpretation of clinical results.

Pseudohypoaldosteronism type 1: clinical features and management in infancy

Type 1 pseudohypoaldosteronism (PHA) is a rare heterogeneous group of disorders characterised by resistance to aldosterone action. There is resultant salt wasting in the neonatal period, with hyperkalaemia and metabolic acidosis. Only after results confirm isolated resistance to aldosterone can the diagnosis of type 1 PHA be confidently made. Type 1 PHA can be further classified into i) renal type 1 (autosomal dominant (AD)) and ii) multiple target organ defect/systemic type 1 (autosomal recessive (AR)). The aim of this case series was to characterise the mode of presentation, management and short-term clinical outcomes of patients with PHA type 1. Case notes of newly diagnosed infants presenting with PHA type 1 were reviewed over a 5-year time period. Seven patients were diagnosed with PHA type 1. Initial presentation ranged from 4 to 28 days of age. Six had weight loss as a presenting feature. All subjects had hyperkalaemia, hyponatraemia, with elevated renin and aldosterone levels. Five patients have renal PHA type 1 and two patients have systemic PHA type, of whom one has had genetic testing to confirm the AR gene mutation on the SCNN1A gene. Renal PHA type 1 responds well to salt supplementation, whereas management of patients with systemic PHA type 1 proves more difficult as they are likely to get frequent episodes of electrolyte imbalance requiring urgent correction.

Acute intermittent porphyria: fatal complications of treatment

Acute neurovisceral attacks of porphyria can be life threatening. They are rare and notoriously difficult to diagnose clinically, but should be considered, particularly in female patients with unexplained abdominal pain, and associated neurological or psychiatric features or hyponatraemia. The diagnosis might be suggested by altered urine colour and can be confirmed by finding an elevated porphobilinogen concentration in fresh urine protected from light. Severe attacks require treatment with intravenous haem arginate and supportive management with safe drugs, including adequate analgesia. Intravenous glucose in water solutions are contraindicated as they aggravate hyponatraemia, which can prove fatal.

Serum 25 hydroxy-vitamin D does not exhibit an acute phase reaction after acute myocardial infarction

Background

There is growing epidemiological evidence linking serum 25 hydroxy-vitamin D (25(OH)D) concentrations to outcome in cardiovascular and other diseases. We have studied patients with acute myocardial infarction (AMI) to determine if they exhibit an acute phase reaction affecting 25(OH)D.

Methods

Patients ( n= 32) with first AMI who had been treated with primary percutaneous coronary intervention within 12 h of symptom onset had venous blood samples taken two days, one week, one month and three months after presentation. Samples were analysed for troponin I, C-reactive protein (CRP) and 25(OH)D.

Results

All patients had significant rises in troponin confirming the myocardial damage and CRP, both of which resolved by 28 days. In contrast, 25(OH)D remained unchanged throughout the 90-day observation period with a median concentration of 46 nmol/L.

Conclusion

Serum 25(OH)D does not change after AMI and is likely to be a reliable marker of vitamin D status in patients with cardiovascular disease.

Consumptive hypothyroidism: a case report and review of the literature

Hepatic haemangioendothelioma is a rare vascular tumour in infants and may be associated with a unique form of thyroid function abnormalities. Hepatic haemangioendotheliomata is capable of producing an excess of the thyroid hormone inactivating enzyme, type 3 iodothyronine deiodinase. The increased enzyme activity leads to rapid degradation of thyroid hormones, resulting in frank hypothyroidism. We report a case of a three-month-old neonate with multiple hepatic haemangioendotheliomata and associated hypothyroidism. The patient required increasing doses of thyroid hormone.

B-type natriuretic peptide in lymphedema

Lymphedema often responds to compression therapy which can also cause undesirable cardiac overload if heart failure coexists. We hypothesized that the biomarker B-type natriuretic peptide (BNP) can be used to screen lymphedema patients for undetected cardiac dysfunction. We studied unselected consecutive patients with lymphedema to determine their BNP status and compared these data with those obtained from healthy subjects without known cardiovascular diseases. Out of a total of 305 subjects with lymphedema screened, 102 (33%) consented to take part in this study. The majority (87%) were female with a mean age of 60.5 +/- 13.2 (SD) years, and 47% had just lower limb swelling. The groups were equally divided between cancer and non-cancer related causes. There were 45 females and 4 males under 60 years old, and 44 female and 9 male patients over 60 years old. Median (IQR) BNP (ng/L) were as follows: <60 years females = 17.9 (15.2) (median [RR: 3 - 64] and males = 12.4 (14.7) [RR: 0.2 - 44], >60 years females = 35.8 (57.9) [RR: 2 -247)] and males = 47.2 (44.1) [RR: 2 - 238]. For this population, the BNP concentration 100 ng/L was adopted as the value to exclude heart failure. Using this definition, 7 lymphedema subjects had BNP concentrations of 120 (19.8) ng/L, and all were found to have cardiac abnormalities on echocardiography. This study demonstrated that 93% of unselected subjects with lymphedema had BNP concentrations that exclude a diagnosis of heart failure. Those subjects with elevated BNP were found on subsequent echocardiography to have cardiac abnormalities. The use of a BNP assay is of potential value in screening patients who are more likely to have cardiac failure. Indicative factors include bilateral leg swelling, over the age of 50 years, breathlessness, where there is no known cause for the swelling. A BNP assay using a BNP concentration threshold of 100 ng/L (29 pmol/L) will identify those patients who require more detailed investigations.

Macroprolactin on the Advia Centaur: experience with 409 patients over a three-year period

Introduction

Macroprolactin (MPRL) is an important source of interference that may lead to misdiagnosis and mismanagement of hyperprolactinaemic patients. Prolactin assays exhibit considerable variation in the detection of MPRL. In this study, we examine the requirement for polyethylene glycol (PEG) precipitation in the analysis of hyperprolactinaemia detected by the Advia Centaur as it has a relatively low reactivity with MPRL.

Methods

Four hundreds and sixty-four hyperprolactinaemic samples were collected from the laboratory information system for Saint James University Hospital over a three-year period. These samples were screened for MPRL using PEG precipitation protocol. Monomeric prolactin concentration post-PEG precipitation was compared with a reference range determined by PEG precipitation in normal subjects.

Results

MPRL was the cause of hyperprolactinaemia in 4% of patients (16/409) over the three-year period studied. Nine subjects with MPRL also had elevated monomeric prolactin.

Conclusions

PEG screening is still needed for assays with low MPRL reactivity such as the Advia Centaur and this should be performed with a locally derived reference range for monomeric prolactin.

Retrospective survey of serum lipids in patients receiving more than three courses of isotretinoin

Isotretinoin is well recognised to cause hyperlipidaemia. This is most obvious during the second month of a 4-month course. Since there are no long-term data on lipid profiles, we have identified 30 subjects who have received 3 or more courses of isotretinoin. They had been exposed to a median of 24.5 months (range 12-103) isotretinoin therapy with a median total cumulative dose of 350 mg/kg (range 152-1221). The median serum cholesterol pre-treatment was 4.6 mmol/L (range 3-6.4). This compared to a median of 4.5 mmol/L (range 3-6.4) just prior to starting the final course. The median triglyceride levels before treatment and pre-final course were 0.8 mmol/L (range 0.3-1.7) and 0.92 mmol/L (range 0.4-2.6) respectively, indicating no significant change in cholesterol or triglyceride concentrations when measured prior to the first and last courses. In addition there was no correlation between cholesterol or triglyceride concentration before the final course of isotretinoin and the total cumulative dose of isotretinoin. We conclude that there appears to be little risk of causing hyperlipidaemia by prolonged therapy with isotretinoin in patients with acne.

Serum 99th centile values for two heart-type fatty acid binding protein assays

Background

We have previously demonstrated that heart-type fatty acid binding protein (H-FABP) is an independent prognostic marker for survival after acute coronary syndrome (ACS). This study aimed to define the 99th centile values for H-FABP as determined with two different assays, and to study the relationship with age, gender and renal function.

Methods

H-FABP was measured on redundant routine outpatient samples using the MARKIT-M (Dainippon) and the Evidence Investigator (Randox) assays.

Results

Two hundred and forty-two subjects with Siemens Ultra-TnI value <0.045 μg/L (99th centile) were studied. In all, 174 subjects had estimated glomerular filtration rate (eGFR) >60 mL/min. The 99th centile values for subjects with eGFR >60 mL/min for the Evidence Investigator H-FABP were 5.3 and 5.8 μg/L and for the MARKIT-M H-FABP were 8.3 and 9.1 μg/L in female and male subjects, respectively. There is an increase in H-FABP with age in subjects with normal renal function for both assays. Gender comparison showed no significant difference for either assay. Comparison of samples showed that subjects with eGFR <60 mL/min showed a median increase of 0.71 μg/L with Evidence Investigator assay and 1.09 μg/L with MARKIT-M assay compared with subjects with eGFR >60 mL/min. Calibration differences were confirmed by cross measurement of calibrators and recombinant H-FABP.

Conclusions

We have defined the 99th centile values for H-FABP in a population of primary and secondary care outpatients that can be used to risk stratify patients with ACS. We have confirmed that H-FABP increases with renal dysfunction and age, but have not confirmed the gender difference previously reported.

Feasibility and benefits of implementing a Slimming on Referral service in primary care using a commercial weight management partner

OBJECTIVES

To assess participation in a costed Slimming on Referral service and identify factors associated with success.

STUDY DESIGN

Simple intervention offering participation in a new service to 100 eligible patients. The setting was two Derby general practices, one inner city and one suburban.

PARTICIPANTS

One hundred and seven patients (mean age 50 years) attending general practice for non-obesity reasons.

INCLUSION CRITERIA

BMI > or = 30, age > or = 18 years, not pregnant, no recent commercial weight management group membership, willingness to attempt weight loss.

METHODS

Patients were offered free attendance at a local Slimming World group for 12 consecutive weeks. Body weight and height were measured at baseline, and questionnaires established perceived health, motivation to lose weight, employment, concerns, responsibilities and well-being. Weight was measured at each group visit. The main outcome measures were: (1) changes in body weight at 12 and 24 weeks, (2) social and demographic factors associated with barriers to enrolment, continued attendance and successful weight loss.

RESULTS

Ninety-one (85%) patients attended a group, with 62 completing 12 weeks. Average weight loss in participants was 5.4 kg (6.4% baseline weight). Forty-seven then chose to self-fund, with 34 (37% original group) completing a further 12 weeks. Average weight loss over the total 24 weeks was 11.1 kg (11.3% baseline weight). Regular attendance was affected by income, financial concerns (independent of actual income), age, perceived importance of weight loss and initial weight loss success. Well-being of patients significantly improved between baseline and both 12 and 24 weeks.

CONCLUSIONS

Collaboration with an appropriate commercial weight management organization offers a feasible weight management option that is either similar to, or better than, other options in terms of attrition, efficacy and cost.

Utility of biochemical screening in the context of evaluating patients with a presumptive diagnosis of osteoporosis

The ageing population is expected to increase the burden of osteoporosis on the health care system. Secondary causes of osteoporosis are found in a proportion of patients. There is much controversy regarding the best work-up for patients who have been diagnosed as having osteoporosis based on bone mineral density. It is difficult to decide where interventions should be targeted both from a patient's perspective and for cost effectiveness. We evaluated the utility of a standard panel (full blood count, plasma viscosity, plasma protein, electrophoresis, urine Bence Jones protein, thyroid function test, bone profile, fasting lipids and liver function test) of biochemical investigations in 327 consecutive patients (287 females, 40 males) referred to the new patient osteoporosis clinic from April 1999 to March 2000. Patients were characterised after measurement of spinal/femoral neck bone mineral density after a dual energy X-ray absorptiometry (DEXA) scan. There were 88 patients with osteoporosis, 91 with osteopenia, 130 had normal bone mineral density and 20 who did not have a bone scan. No case of multiple myeloma was found in this cohort of patients. There was no difference in the mean plasma viscosity of patients with and without osteoporosis (P=0.182). There was no significant difference in the abnormal urine calcium/creatinine (Ca/Cr ratio) in patients with osteoporosis and those without osteoporosis (P=0.316). There was no significant difference in the prevalence of hypothyroidism (P=0.213) or thyrotoxicosis (P=0.138) in patients with and without osteoporosis. There was no strong correlation between cholesterol concentrations and osteoporosis (r=0.069). We found no utility in performing a myeloma screen. A small proportion of patients had abnormalities of calcium homeostasis or thyroid disease. We recommend that a screening biochemical evaluation should be restricted to calcium/bone profile and thyroid function tests in patients with a presumptive diagnosis of osteoporosis.

Empowering primary care to tackle the obesity epidemic: the Counterweight Programme

OBJECTIVE

To improve the management of obese adults (18-75 y) in primary care.

DESIGN

Cohort study.

SETTINGS

UK primary care.

SUBJECTS

Obese patients (body mass index > or =30 kg/m(2)) or BMI> or =28 kg/m(2) with obesity-related comorbidities in 80 general practices.

INTERVENTION

The model consists of four phases: (1) audit and project development, (2) practice training and support, (3) nurse-led patient intervention, and (4) evaluation. The intervention programme used evidence-based pathways, which included strategies to empower clinicians and patients. Weight Management Advisers who are specialist obesity dietitians facilitated programme implementation.

MAIN OUTCOME MEASURES

Proportion of practices trained and recruiting patients, and weight change at 12 months.

RESULTS

By March 2004, 58 of the 62 (93.5%) intervention practices had been trained, 47 (75.8%) practices were active in implementing the model and 1549 patients had been recruited. At 12 months, 33% of patients achieved a clinically meaningful weight loss of 5% or more. A total of 49% of patients were classed as 'completers' in that they attended the requisite number of appointments in 3, 6 and 12 months. 'Completers' achieved more successful weight loss with 40% achieving a weight loss of 5% or more at 12 months.

CONCLUSION

The Counterweight programme provides a promising model to improve the management of obesity in primary care.

The British Cardiac Society Working Group definition of myocardial infarction: implications for practice

OBJECTIVE

To assess the impact on observed mortality of the British Cardiac Society (BCS) definition of myocardial infarction (MI) in 11 UK hospitals.

DESIGN

Prospective observational registry.

SETTING

11 adjacent hospitals in the West Yorkshire region.

PATIENTS

2484 patients with the acute coronary syndrome (ACS) were identified during a six month period (28 April to 28 October 2003). Demographic, clinical, and treatment variables were collected on all patients. Deaths were monitored through the Office of National Statistics. Patients were categorised into three groups according to the BCS definition of MI: ACS with unstable angina (UA), ACS with myocyte necrosis, and ACS with clinical MI.

RESULTS

30 day mortality was 4.5%, 10.4%, and 12.9% (p < 0.001) in the ACS with UA, ACS with myocyte necrosis, and ACS with clinical MI groups, respectively. At six months the mortality for patients in the groups ACS with clinical MI and ACS with myocyte necrosis was similar (19.2% v 18.7%), being higher than for ACS with UA (8.6%). Same admission percutaneous coronary intervention was similar in groups with clinical MI and myocyte necrosis (11.1% v 10.7%, respectively) as was coronary artery bypass grafting (2.6% v 2.7%, respectively). However, these two groups differed significantly in the prescribing of secondary prevention (aspirin, 79% v 69%; statins, 80% v 68%; beta blockers, 66% v 53%; and angiotensin converting enzyme inhibitors, 65% v 53%; p < 0.001).

CONCLUSIONS

At 30 days the new BCS categories for MI predict three distinct outcomes. However, within a contemporary UK population this was no longer apparent at six months, as mortality for patients with ACS with myocyte necrosis had risen to the same level as those for patients with ACS with clinical MI. One possible explanation for this is the apparent under use of drugs known to improve prognosis after traditionally defined MI.

Hereditary coproporphyria: comparison of molecular and biochemical investigations in a large family

Hereditary coproporphyria (HCP) is the least common of the three autosomal dominant acute porphyrias. To compare the sensitivity of metabolite measurements for the identification of asymptomatic HCP, we carried out a molecular and biochemical investigation of a large family in which HCP is caused by a previously unreported frameshift mutation (c.119delA). Thirteen of 19 asymptomatic family members, aged 10-72 years, were shown by mutational analysis to have HCP. The faecal coproporphyrin isomer III:I ratio was increased in all of these 13 family members; faecal total porphyrin concentration and urinary porphyrin excretion were increased in 11 and 8 of them, respectively. Plasma porphyrin concentrations were marginally increased in three individuals and plasma fluorescence emission scanning showed a porphyrin peak at 618 nm in two of these. Our results add to the evidence that an increased faecal porphyrin coproporphyrin III:I ratio is a highly sensitive test for the detection of clinically latent HCP in individuals over the age of 10 years; its sensitivity below this age remains uncertain. They also show that plasma fluorescence emission scanning is not useful for the investigation of families with HCP.

Prolactin and macroprolactin: a case report of hyperprolactinaemia highlighting the interpretation of discrepant results

Immunoassay methods for prolactin detect macroprolactin (i.e. high molecular mass complexes of prolactin) to various degrees. Therefore it is generally assumed that the widely differing results by methods that measure both moieties to a differing extent are due to the presence of macroprolactin. We present a case which challenges such an assumption and suggest that precipitation by polyethylene glycol is the most reliable screen for identifying macroprolactin (and/or interfering antibodies if present).

A survey of laboratory 'critical (alert) limits' in the UK

INTRODUCTION

Critical or alert limits are the values of laboratory measurements that are regarded as requiring urgent clinical action and should be communicated to a clinician urgently. Despite this, there has been little evaluation of these values in the UK.

METHODS

We have conducted a survey of hospital biochemistry laboratories in the UK.

RESULTS

Ninety-four laboratories responded to the questionnaire; the response rate was not recorded. Twenty-three laboratories had derived their action limits locally from a consensus with their clinicians, experience over many years, and the literature. Only two laboratories quoted literature to support their values. Seven laboratories did not submit actual critical values. There was considerable variance in the values defined as critical by the responding laboratories.

DISCUSSION

Each laboratory needs to evaluate its own list of acutely important critical values and aim for a small number of analytes that are always communicated to the doctor, so that clinical needs are met without raising the risk of information overload.

Evaluation of whole blood serotonin and plasma and urine 5-hydroxyindole acetic acid in diagnosis of carcinoid disease

BACKGROUND

Carcinoid disease is an uncommon disorder resulting from tumours of the enterochromaffin cells. Current biochemical investigation usually involves the measurement of 5-hydroxyindole-3-acetic acid (5-HIAA) in 24-h urine collections. Because of the problems associated with urine collections (i.e. inconvenience, accuracy of collection and requirement for preservatives) two alternative markers, fasting plasma 5-HIAA and whole blood serotonin (5-hydroxytryptamine), have been studied.

METHODS AND RESULTS

Whole blood serotonin concentration and plasma and urine 5-HIAA concentrations were measured by high-performance liquid chromatography in 31 patients suspected of having carcinoid and 26 known carcinoid patients. Receiver operator characteristic curve analysis of the data showed no statistical difference between the three markers (P>0.01) with regard to their discriminating function. However, fasting plasma 5-HIAA assay showed greater stability than whole blood serotonin assay and is more convenient for the patient than a 24-h urine collection. At a cut-off value of 118 nmol/L plasma 5-HIAA assay showed a sensitivity of 89%, a specificity of 97% and a test efficiency of 93%. Whole blood serotonin assay was further limited by its saturation in platelets at 40 nmol/10(9) platelets which made it less suitable for monitoring the treatment of carcinoid disease.

CONCLUSION

Fasting plasma 5-HIAA concentration provides a more convenient screening test for carcinoid and overcomes the problems associated with 24-h urine collections, without any loss of diagnostic precision.

Severe hypertriglyceridaemia associated with human immunodeficiency virus and highly active antiretroviral therapy

We report two cases of severe hypertriglyceridaemia associated with human immunodeficiency virus infection and highly active antiretroviral therapy (HAART). The first patient, a 39-year-old man, developed moderate hypertriglyceridaemia (5.88 mmol/L) and hypercholesterolaemia (7.0 mmol/L) after 8 months of HAART. When his therapy was altered, triglyceride and cholesterol concentrations increased further to 15.9 and 10.9 mmol/L, respectively, after 6 weeks. The second patient, a 31-year-old man, presented with triglyceride and cholesterol concentrations of 16.2 and 5.7 mmol/L, respectively, following an 8-year history of HAART. Therapy was changed, but 1 month later the triglyceride concentration had increased to 39.4 mmol/L and the cholesterol concentration to 12.1 mmol/L. Both patients were managed by a change in HAART and the introduction of a fibric acid derivative. Although neither patient displayed any clinical symptoms associated with hypertriglyceridaemia, it is important to recognize such cases because of the associated risk of pancreatitis and coronary disease.

Interference in immunoassay is an underestimated problem

The presence of antibodies in some patients' serum has long been known to be a potential source of interference in immunoassays, as shown by numerous case reports. These often appear after the introduction of a new analyte (e.g. troponin) and then decrease in number as the topic becomes exhausted. This highlights the persistent and intrinsic nature of this problem, despite attempts by the manufacturers to compensate for this source of error. However, an explanation of the immunoanalytical basis underpinning these assays could be more effective in raising awareness than intermittent case reports. In this review we have outlined the use of antibodies as reagents, the factors determining how they bind to antigen(s), and the nature of the immune response in order to explain the insidious and unpredictable nature of this form of interference. Studies on the prevalence of interference have yielded values ranging from 0.05 to more than 2%. However, these figures are analyte- and assay-specific, influenced by the study design, and are not therefore generally applicable. It is also highly likely that figures on prevalence and incidence will worsen in the future because of the wider use of monoclonal antibodies as diagnostic and therapeutic tools. Clinical laboratories should be alert to assay interference from antibodies irrespective of its nature, as immunoassays will remain an indispensable analytical tool, unlikely to be replaced in the foreseeable future by a practical alternative.