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.

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

UNLABELLED: 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.

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.

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.

The hook effect: a need for constant vigilance.

The hook effect is a well-recognized problem that can occur in assays of most tumour markers, including alpha feto-protein (AFP). We present a case of hepatoblastoma in a baby. The diagnosis was delayed as a result of unrecognized 'hooking' of a very high AFP concentration in the automated immunoassay method used. The falsely low result obtained was considered normal for the patient's age and supported the diagnosis of benign haemangioendothelioma. Liaison between clinical and laboratory staff was critical in obtaining an accurate AFP result, proceeding to liver biopsy and establishing the definitive diagnosis of hepatoblastoma. While the reasons and solutions for hook effect have been well researched and published, we believe the presence of extremely high serum AFP concentration in some hepatoblastoma patients means that the hook effect remains a problem and can generate erroneously low AFP results despite assay reformulation by manufacturers. Therefore constant vigilance by laboratory staff is still needed.

Loss of expression of oestrogen receptor beta in colon cancer and its association with Dukes' staging.

Gender differences in the incidence and behaviour of colon cancer suggest a hormonal influence and epidemiological data suggest a protective effect for hormone replacement therapy. Recently, it has been shown that oestrogen receptor (ER) beta is the predominant ER in colon tissue. The aim of this study was to examine the expression and distribution of ERbeta in normal and colorectal cancer samples, using immunohistochemistry and (in a subset of patients) real-time quantitative reverse transcriptase polymerase chain reaction in a well-defined patient cohort and to correlate this with clinico-pathological outcome. Immunohistochemical analyses of normal colon revealed strong specific nuclear immuno-reactivity in all epithelial cells lining the colonic crypts. In colon cancer, ERbeta expression was lost in 21% of samples irrespective of patient age or gender. Interestingly loss of ERbeta expression was higher in left colon and rectal cancers (27%) compared to right colon cancers (8%). A correlation between loss of ERbeta expression and advanced Dukes stage was observed. Loss of ERbeta with increased Dukes' stage suggests that it may be affording a protective effect against colon carcinogenesis. Its presence may be a favourable prognostic marker in this disease and could explain the protective effect of oestrogens against colon cancer development.

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).