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  • Author: Julian H. Barth x
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Abstract

Background:

It is now recommended that all samples with raised prolactin should be examined for the presence of macroprolactin. We performed a retrospective review of our experience of macroprolactin to determine the incidence and the natural history of macroprolactin.

Methods:

A retrospective study of macroprolactin was made in a large clinical laboratory. Macroprolactin was measured on those samples where it is requested and where the total prolactin is >1000 mIU/L. Prolactin was measured using the Siemens Centaur and macroprolactin was measured following polyethylene glycol (PEG)-precipitation.

Results:

The incidence of macroprolactin in samples where the total prolactin was >1000 mIU/L was 36/670 (5.4%). During this period, 12,064 samples were received for prolactin analysis. Over the period since 2006, 22 subjects had a sample with an isolated macroprolactin measurement followed by another sample without macroprolactin after a median period of 0.46 years. Twenty-five subjects had multiple consecutive measurements of macroprolactin lasting a median period of 2.1 years. Fourteen subjects had more than six samples which had been subjected to PEG precipitation. In these subjects, the reproducibility of PEG precipitation over a median of 6 years was 1.1% CV (recovery 75% [26–110] (median [range])).

Conclusions:

The presence of macroprolactin can change over time and we cannot advise that once a test for macroprolactinemia has been performed that it is not necessary to repeat the investigation if a subsequent sample is hyperprolactinemic; nor can one assume that macroprolactin will not develop even if it has been excluded previously.

Abstract

Clinical practice guidelines (CPG) are written with the aim of collating the most up to date information into a single document that will aid clinicians in providing the best practice for their patients. There is evidence to suggest that those clinicians who adhere to CPG deliver better outcomes for their patients. Why, therefore, are clinicians so poor at adhering to CPG? The main barriers include awareness, familiarity and agreement with the contents. Secondly, clinicians must feel that they have the skills and are therefore able to deliver on the CPG. Clinicians also need to be able to overcome the inertia of “normal practice” and understand the need for change. Thirdly, the goals of clinicians and patients are not always the same as each other (or the guidelines). Finally, there are a multitude of external barriers including equipment, space, educational materials, time, staff, and financial resource. In view of the considerable energy that has been placed on guidelines, there has been extensive research into their uptake. Laboratory medicine specialists are not immune from these barriers. Most CPG that include laboratory tests do not have sufficient detail for laboratories to provide any added value. However, where appropriate recommendations are made, then it appears that laboratory specialist express the same difficulties in compliance as front-line clinicians.

Abstract

Background: The implementation of national and international guidelines is beginning to standardise clinical practice. However, since many guidelines have decision limits based on laboratory tests, there is an urgent need to ensure that different laboratories obtain the same analytical result on any sample. A scientifically-based quality control process will be a pre-requisite to provide this level of analytical performance which will support evidence-based guidelines and movement of patients across boundaries while maintaining standardised outcomes. We discuss the finding of a pilot study performed to assess UK clinical laboratories readiness to work to a higher grade quality specifications such as biological variation-based quality specifications.

Methods: Internal quality control (IQC) data for HbA1c, glucose, creatinine, cholesterol and high density lipoprotein (HDL)-cholesterol were collected from UK laboratories participating in the Bio-Rad Unity QC programme. The median of the coefficient of variation (CV%) of the participating laboratories was evaluated against the CV% based on biological variation.

Results: Except creatinine, the other four analytes had a variable degree of compliance with the biological variation-based quality specifications. More than 75% of the laboratories met the biological variation-based quality specifications for glucose, cholesterol and HDL-cholesterol. Slightly over 50% of the laboratories met the analytical goal for HBA1c. Only one analyte (cholesterol) had a performance achieving the higher quality specifications consistent with 5σ.

Conclusions: Our data from IQC do not consistently demonstrate that the results from clinical laboratories meet evidence-based quality specifications. Therefore, we propose that a graded scale of quality specifications may be needed at this stage.

Abstract

Several studies have shown that recommendations related to how laboratory testing should be performed and results interpreted are limited in medical guidelines and that the uptake and implementation of the recommendations that are available need improvement. The EFLM/UEMS Working Group on Guidelines conducted a survey amongst the national societies for clinical chemistry in Europe regarding development of laboratory-related guidelines. The results showed that most countries have guidelines that are specifically related to laboratory testing; however, not all countries have a formal procedure for accepting such guidelines and few countries have guideline committees. Based on this, the EFLM/UEMS Working Group on Guidelines conclude that there is still room for improvement regarding these processes in Europe and raise the question if the accreditation bodies could be a facilitator for an improvement.

Abstract

Background: Correct information provided by guidelines may reduce laboratory test related errors during the pre-analytical, analytical and post-analytical phase and increase the quality of laboratory results.

Methods: Twelve clinical practice guidelines were reviewed regarding inclusion of important laboratory investigations. Based on the results and the authors’ experience, two checklists were developed: one comprehensive list including topics that authors of guidelines may consider and one consisting of minimal standards that should be covered for all laboratory tests recommended in clinical practice guidelines. The number of topics addressed by the guidelines was related to involvement of laboratory medicine specialists in the guideline development process.

Results: The comprehensive list suggests 33 pre- analytical, 37 analytical and 10 post-analytical items. The mean percentage of topics dealt with by the guidelines was 33% (median 30%, range 17%–55%) and inclusion of a laboratory medicine specialist in the guideline committee significantly increased the number of topics addressed. Information about patient status, biological and analytical interferences and sample handling were scarce in most guidelines even if the inclusion of a laboratory medicine specialist in the development process seemingly led to increased focus on, e.g., sample type, sample handling and analytical variation. Examples underlining the importance of including laboratory items are given.

Conclusions: Inclusion of laboratory medicine specialist in the guideline development process may increase the focus on important laboratory related items even if this information is usually limited. Two checklists are suggested to help guideline developers to cover all important topics related to laboratory testing.

Abstract

Background: As a part of an International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) project to prepare a commutable reference material for cardiac troponin I (cTnI), a pilot study evaluated current cTnI assays for measurement equivalence and their standardization capability.

Methods: cTnI-positive samples collected from 90 patients with suspected acute myocardial infarction were assessed for method comparison by 16 cTnI commercial assays according to predefined testing protocols. Seven serum pools prepared from these samples were also assessed.

Results: Each assay was assessed against median cTnI concentrations measured by 16 cTnI assays using Passing-Bablok regression analysis of 79 patient samples with values above each assay’s declared detection limit. We observed a 10-fold difference in cTnI concentrations for lowest to highest measurement results. After mathematical recalibration of assays, the between-assay variation for patient samples reduced on average from 40% to 22% at low cTnI concentration, 37%–20% at medium concentration, and 29%–14% at high concentration. The average reduction for pools was larger at 16%, 13% and 7% for low, medium and high cTnI concentrations, respectively. Overall, assays demonstrated negligible bias after recalibration (y-intercept: –1.4 to 0.3 ng/L); however, a few samples showed substantial positive and/or negative differences for individual cTnI assays.

Conclusions: All of the 16 commercial cTnI assays evaluated in the study demonstrated a significantly higher degree of measurement equivalence after mathematical recalibration, indicating that measurement harmonization or standardization would be effective at reducing inter-assay bias. Pooled sera behaved similarly to individual samples in most assays.

Abstract

Background:

Optimum patient care in relation to laboratory medicine is achieved when results of laboratory tests are equivalent, irrespective of the analytical platform used or the country where the laboratory is located. Standardization and harmonization minimize differences and the success of efforts to achieve this can be monitored with international category 1 external quality assessment (EQA) programs.

Methods:

An EQA project with commutable samples, targeted with reference measurement procedures (RMPs) was organized by EQA institutes in Italy, the Netherlands, Portugal, UK, and Spain. Results of 17 general chemistry analytes were evaluated across countries and across manufacturers according to performance specifications derived from biological variation (BV).

Results:

For K, uric acid, glucose, cholesterol and high-density density (HDL) cholesterol, the minimum performance specification was met in all countries and by all manufacturers. For Na, Cl, and Ca, the minimum performance specifications were met by none of the countries and manufacturers. For enzymes, the situation was complicated, as standardization of results of enzymes toward RMPs was still not achieved in 20% of the laboratories and questionable in the remaining 80%.

Conclusions:

The overall performance of the measurement of 17 general chemistry analytes in European medical laboratories met the minimum performance specifications. In this general picture, there were no significant differences per country and no significant differences per manufacturer. There were major differences between the analytes. There were six analytes for which the minimum quality specifications were not met and manufacturers should improve their performance for these analytes. Standardization of results of enzymes requires ongoing efforts.

Abstract

Quality indicators (QIs) are fundamental tools for enabling users to quantify the quality of all operational processes by comparing it against a defined criterion. QIs data should be collected over time to identify, correct, and continuously monitor defects and improve performance and patient safety by identifying and implementing effective interventions. According to the international standard for medical laboratories accreditation, the laboratory shall establish and periodically review QIs to monitor and evaluate performance throughout critical aspects of pre-, intra-, and post-analytical processes. However, while some interesting programs on indicators in the total testing process have been developed in some countries, there is no consensus for the production of joint recommendations focusing on the adoption of universal QIs and common terminology in the total testing process. A preliminary agreement has been achieved in a Consensus Conference organized in Padua in 2013, after revising the model of quality indicators (MQI) developed by the Working Group on “Laboratory Errors and Patient Safety” of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). The consensually accepted list of QIs, which takes into consideration both their importance and applicability, should be tested by all potentially interested clinical laboratories to identify further steps in the harmonization project.

Abstract

Reference intervals are a vital part of the information supplied by clinical laboratories to support interpretation of numerical pathology results such as are produced in clinical chemistry and hematology laboratories. The traditional method for establishing reference intervals, known as the direct approach, is based on collecting samples from members of a preselected reference population, making the measurements and then determining the intervals. An alternative approach is to perform analysis of results generated as part of routine pathology testing and using appropriate statistical techniques to determine reference intervals. This is known as the indirect approach. This paper from a working group of the International Federation of Clinical Chemistry (IFCC) Committee on Reference Intervals and Decision Limits (C-RIDL) aims to summarize current thinking on indirect approaches to reference intervals. The indirect approach has some major potential advantages compared with direct methods. The processes are faster, cheaper and do not involve patient inconvenience, discomfort or the risks associated with generating new patient health information. Indirect methods also use the same preanalytical and analytical techniques used for patient management and can provide very large numbers for assessment. Limitations to the indirect methods include possible effects of diseased subpopulations on the derived interval. The IFCC C-RIDL aims to encourage the use of indirect methods to establish and verify reference intervals, to promote publication of such intervals with clear explanation of the process used and also to support the development of improved statistical techniques for these studies.