Sandra Secchiero

Troponin T as a marker of ischemic myocardial injury.

A study was undertaken to evaluate the clinical relevance of serum troponin T (TnT) as a marker of ischemic myocardial injury, using a new automated enzyme immunoassay. The reference range for serum TnT was established by measuring serum TnT concentrations in blood obtained from 262 healthy subjects. The serum concentration of TnT was compared to serum creatine kinase activity, creatine kinase MB (mass and activity), myoglobin concentration, and lactate dehydrogenase activity: in 77 patients with myocardial infarction (55 received thrombolytic treatment); in 32 patients with unstable angina; in 30 patients with nonischemic heart diseases; and in 40 patients with skeletal muscle injuries. Our findings showed that: a) 99% of healthy blood donors had TnT concentrations < 0.10 micrograms/L; b) the test had a high clinical efficiency in the diagnosis of acute myocardial infarction, with a sensitivity of 1.0 and a specificity of 0.88 at a decision level of 0.20 micrograms/L; c) serum TnT had a later peak value (8-38 h), but a wider diagnostic window (> 126 h) than the traditional markers considered in the study; d) serum TnT had an excellent sensitivity in the detection of microinfarctions in patients with unstable angina pectoris; e) the release patterns of serum TnT were qualitatively different in perfused versus nonperfused patients. Peak serum TnT values and time to peak values were statistically different (p = 0.0336 and p = 0.0001) in reperfused and nonreperfused AMI patients, respectively; f) a ratio of serum TnT at 16 h to serum TnT at 32 h after chest pain > 1 provided a good indication of reperfusion in thrombolytic treatment (94% efficiency).

External Quality Assessment Schemes: need for recognised requirements

Programs for Accreditation of clinical laboratories consider participation in External Quality Assessment Schemes (EQAS) a key element in the evaluation of testing procedures and improving them. One of the main functions of EQAS is to assess whether laboratories perform tests competently. It is therefore of utmost importance for laboratories to participate in EQAS that are in line with formally recognised requirements. Specific proposals have been made on how to design and execute EQAS by International Working Groups, but there seems to be no consensus on the best strategies to use and quality specifications to set out. The Clinical Pathology Accreditation (CPA) Program for EQA Scheme Accreditation (CPA-EQA) is the only program in Europe to provide a formal recognition of the quality of EQAS activities. The present paper reports on the experience of the Centre of Biomedical Research which is following an accreditation process for their own schemes in line with the CPA-EQA program and a proposal to set requirements that Italian schemes must follow to be recognised as valid and effective.

Risk management in laboratory medicine: quality assurance programs and professional competence

Abstract To guarantee excellent performance and service, the process of identifying and treating error risks must be integrated into the total testing process. Quality Assurance Programs (QAPs) represent an important tool that allows us to identify errors and pinpoint any need for further systematic investigations, and to rectify procedures to improve the inputs and processes by which the service is delivered. The models used by the laboratory to assure quality and manage the risk of errors have been modified in line with an approach in which the identification of quality goals and the redefinition of professionals duties and responsibilities are indispensable. Error risk is currently high in some areas of laboratory activity, and QAP is needed now more than ever. The present paper provides some descriptive examples of an approach that can be followed to manage an External Quality Assessment Scheme (EQAS) and quality indicators (QIs), the main tools used by laboratories to assure the quality of their service, for the prevention of error risk. In particular, we describe the correct approach to choose EQAS, to use information from the EQAS report, to design a QI model, and to analyze any QI data. The examples highlight that any well-designed quality system can be ineffective if it is not managed by highly competent professionals with a deep sense of responsibility. Clin Chem Lab Med 2007;45:756–65.

Serum arylesterase (paraoxonase) activity following myocardial infarction

Arylesterase (Aryl-ester hydrolase, paraoxonase, E.C. 3.1.1.2) hydrolyzes paraoxone, the active metabolite of the organophosphorous insecticide parathione, into p-nitrophenol and diethylphosphate. Although the natural substrate remains unknow, calcium (Ca’+) is known to be an essential co-factor [l]. The arylesterase assay was clinically applied in the histochemistry of tumors [2], hepatic diseases [3] and poisoning by organophosphates [4). Association between arylesterase and high-density lipoproteins (HDL) [5] has caused investigation of serum enzyme activity following myocardial infarction [6] to indirectly assess HDL concentration. Our study has two aims: (a) to confirm the association between serum arylesterase and HDL, which may play a protective role against coronary atherosclerosis; (b) to verify if in acute myocardial infarction variations of enzymatic activity occur which might have prognostic value.

Monitoring skeletal cancer metastases with the bone isoenzyme of tissue unspecific alkaline phosphatase.

The efficacy of bone alkaline phosphatase (ALP) isoenzyme measurement using lectin precipitation in confirming metastatic bone lesions was compared with total ALP and osteocalcin assay in serum. Sixty-five patients with cancer and metastases to bone (n = 44), liver (n = 15) or lymph nodes (n = 6) as well as 33 healthy adults were studied. Assay of bone ALP is as sensitive but more specific than assay of total ALP in the identification of bone metastases. On the other hand, bone ALP did not correlate with osteocalcin, as is the case in other bone diseases. In the serial monitoring of nine patients with skeletal metastases, bone ALP correlated well with the presence of pain and the progression or regression of metastatic spread.

Reference intervals: are interlaboratory differences appropriate?

In laboratory medicine, analytical results and their relative reference intervals (RI) represent the terms of a binomial that makes a report effective. If gross errors are neglected, an analytical result is subject to two kinds of error: inaccuracy and imprecision. A hierarchy of models has to be applied to set analytical specifications, starting from the evaluation of the effect of analytical performance on clinical outcomes in specific clinical setting (1). This now applies only to few analytes. Instead, the evaluation of the effect of analytical performance on clinical decision and, in particular, data based on components of biological variation is applicable to a wide range of analytes (2). The reference intervals may be related to the results, which means that they are compromised by the same degree of relative inaccuracy. It has been proven that only with the adoption of an appropriate reference range we can obtain a clinically effective report. The recommendation that the single laboratory should calculate the “proper” RI springs from the need to make the relative RI “appropriate”. To verify the appropriateness of RI we evaluated data from the External Quality Assessment scheme (EQA) managed by the Biomedical Research Centre (160 laboratories, mainly in the Veneto area). To identify homogeneous groups of methods, the Centre requires from participant laboratories not only methodological information, but also the reference ranges used (in fact the results are sent from laboratories to the Centre as a patient report). Only a few analytes, are presented and discussed as examples. Despite its importance as risk factor for atherosclerosis and myocardial infarction, there are significant differences in the reference intervals used for cholesterol by the laboratories that use the same analytical methods (Table 1). About a third of the laboratories use the so-called “desirable value” (5.18 mmol/l) as the upper limit, but others use an upper limit as high as 7.25 mmol/l. These differences would be less serious if they were related to a different relative accuracy. However, the results from laboratories participating in the EQA were very similar. For instance, for the control sample 6B, the mean value (consensus value) was 6.79 mmol/l and standard deviation (SD) was 0.28 mmol/l. If this had been a sample from a real patient, the report would have been “normal” according to some laboratories and “abnormally high” according to others. Clearly, many laboratories erroneously use the populationbased reference intervals. Although to a lesser extent, some differences were found for glucose. In some laboratories the lower limit is so high (Table 2) that they should classify the control sample 5A (mean ± SD = 3.33 ± 0.17 mmol/l) as “hypoglycemia.” The differences in reference intervals used for sodium are large (Table 3) ranging from 130–140 mmol/l to 130–160 mmol/l. The most widely used range is 135–145 mmol/l (17% of the laboratories), but the second most widely used is 50% larger (135–150 mmol/l). Also in this case, the low interlaboratory inaccuracy is not consistent with different reference values, Tab. 1 Values for cholesterol obtained on control sample 6B: mean ± SD = 6.79 ± 0.28 mmol/l.

Recommendations for the routine use of pancreatic amylase measurement instead of total amylase for the diagnosis and monitoring of pancreatic pathology.

Abstract This document reviews the scientific evidence expected to persuade clinical laboratories to substitute pancreatic amylase measurement for total amylase in cases of suspected pancreatic pathology. A substantial evidence is now available to support such change. The measurement of pancreatic amylase in serum is: 1. more sensitive and specific for the detection of pancreatic tissue damage than that of the total enzyme activity, 2. easy and quick to perform in emergency conditions, 3. analytically precise in relation to its clinical application, 4. suitable for easy transfer and comparison of results from different care delivery units, and 5. characterized by welldefined decision limits for the diagnosis of acute pancreatitis.

Troponin T, creatine kinase MB mass, and creatine kinase MB isoform ratio in the detection of myocardial damage during non-surgical coronary revascularization

The presence of myocardial injury during non-surgical coronary revascularization has been evaluated by means of highly specific and sensitive biochemical markers. Troponin T, creatine kinase-MB isoenzyme mass concentration, and creatine kinase MB2/MB1 isoform ratio have been determined in 80 patients who underwent coronary revascularization with percutaneous transluminal coronary angioplasty (PTCA). Forty-five patients underwent balloon angioplasty, 15 rotational atherectomy, 10 directional atherectomy, and 10 elective coronary stenting. Serum concentration of the evaluated markers did not increase significantly after 57 uncomplicated revascularization procedures, including 15 rotablation procedures, nor after 8 PTCAs complicated by localized coronary type B and C dissections. Significant elevation of all markers above the upper limits of the reference interval (P < 0.05) was detected after occlusion of small side branches (< 0.5 mm diameter) in 5 patients. Creatine kinase MB2/MB1 isoform ratio was the earliest marker to increase. After recanalization of occluded vessels in 8/10 patients with 6-60 days old myocardial infarction only troponin T concentrations increased from a baseline of 0.28 microgram/l to a median peak of 0.80 microgram/l. This increase was statistically not significant (P = 0.12). In conclusion, myocardial damage was not detected following uncomplicated non-surgical revascularization obtained with different techniques. Markers of myocardial injury provide high sensitivity after small side branch occlusion.

An Italian external quality assessment (EQA) program on urinary sediment.

BACKGROUND EQA programs on urinary sediment are rare. We describe an EQA Italian program which started in 2001 and involves today more than 300 laboratories. METHODS The program, which started with a questionnaire about the methodological aspects on urinary sediment, includes today four surveys per year. These ask the participants the identification and clinical associations of urinary sediment particles shown by colour images (surveys 1 and 3) and the diagnosis of clinical cases presented by both images and a short clinical history (surveys 2 and 4). The results of each survey are then scored and commented. RESULTS Questionnaire (participants = 287): most methodological aspects were not dealt with properly. IDENTIFICATION cells, lipids, casts and some contaminants were poorly known. However, when 27 particles were presented for the second time and 16 particles for the third time, the correct identification rate for most of them increased significantly. Clinical associations (No presented = 16): a correct answer was indicated by > or = 84% of participants for all particles but one. Clinical cases (No presented=4): lowest correct identification for urine contamination from genital secretion (77.3%), highest for ureteric stone (94.4%). CONCLUSIONS Our program shows that EQA programs are both useful and needed.

Analytical performance of 17 general chemistry analytes across countries and across manufacturers in the INPUtS project of EQA organizers in Italy, the Netherlands, Portugal, United Kingdom and Spain

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.