[State of the art and method validations: application to fidelity performance]. / Etat de l'art et validation de techniques: application aux performances de fidélité

Current events of clinical laboratories in France argue a lot about quality management. Setting up an assurance quality system can be realized in many approaches listed by increasing requirements: respect of reglementary Guide de bonne exécution des analyses (GBEA), BioQualite qualification, certification and at last accreditation. This last step corresponds to the recognition of the competence of the laboratory to execute specifics tasks. Validation of methods used in the laboratory is a key point when you realize an accreditation package. Fidelity (repetability and reproductibility) is one of the parameters to check in your lab for quantitative methods. These performances are validated in comparison with targets beforehand defined (according to biological variation or state of the art). This article reports fidelity performances obtained in 2000 and 2006 by the participants to ProBioQual internal quality controls. Considering these performances obtained in routine conditions, the different possible approaches to define acceptability limits were discussed.

[About the choice of acceptability limits in external quality assessment schemes]. / Réflexion sur le choix des limites acceptables dans les programmes d'évaluation externe de la qualité

Quality control schemes are a practical tool used in clinical laboratories and an essential element for any quality assurance process. In France, external quality assessment schemes (EQAS) can be mandatory (as national quality control organized by AFSSAPS) or voluntary as those suggested by French associations (ProBioQual, CTCB or Asqualab). These EQAS usually evaluate participants according to their performances: this ranking depends on acceptability limits which are here compared. Various examples based on ProBioQual's background illustrate difficulties to plan out analytical quality specifications. A comment is given about the best criteria (state of the art or biological variation mainly) to be considered to delimit analytic goals. This discussion includes approaches suggested by French committee on accreditation (Cofrac). All criteria could be criticized but it is important to compare oneself laboratory to peers and also to take account of biological variation.

[Blood screening of benzodiazepines and tricyclic antidepressants. Results of 5 years of interhospital controls]. / Dépistage des benzodiazepines et des antidepresseurs tricycliques dans le serum. Bilan de cinq ans de contröles inter hospitaliers.

Pro bio Qual Association of Lyon have proposed a control which include the control for detecting benzodiazepines (BZD) and tricyclic antidepressants (ADT) since 2000. With this control, we have evaluated the specificity and the sensitivity of techniques used. We have tested the maprotiline reactivity too (tetracyclic antidepressant). We report results achieved with different immunoassay methods and their performances: specificity and sensitivity. The number of laboratories which realize these analyses is constant: these laboratories are hospital laboratories. Two methods are most common used: the fluorescence polarization immunoassay (FPIA) and the enzyme multiplied immunoassay test (EMIT). The evolution of these techniques does square with the evolution of chemistry analysers used in hospital laboratories. For the BZD, the specificity is good. For the ADT, carbamazepine at low concentration (5 mg/L) gives a positive result with FPIA Abbott assay; carbamazepine at high concentration (25 mg/L) gives a negative result with EMIT assay; phenothiazines give a positive response. For the BZD, the analyser Integra gives best results of sensitivity. Results of sensitivity obtained with the kit EMIT DAU are better than results obtained with the kit EMIT Serum. For the ADT, results of sensitivity obtained with FPIA Abbott assay seem better; the adaptation of EMIT assay on Integra analyser gives less good results. The reactivity for the BZD is very different: we can ignore a severe intoxication with alprazolam or lorazepam (response << cut off) but we can give a positive result for a therapeutic concentration of diazepam for example. With ADT, we haven't the same problem. But the reactivity for nortriptyline is less good than the reactivity for amitriptyline. So we should use a "cut off" concentration which corresponds to the best sensitivity and the best specificity.

[Digoxin assay: results of 10 years of intralaboratory controls]. / Dosage de la digoxine: exploitation de 10 ans de contrôles interlaboratoires.

Serum digoxin measurement is often performed in medical laboratories. A professional association specialized in quality control, based in Lyon, has been organizing punctual controls of medication measurement for the past ten years. The results are analysed in term of intra and inter-technique precision, difference between methods and specificity in regard to endogenous or exogenous interfering substances. Methods have changed with a quasi disappearance of the methods used ten years ago (FPIA, EMIT) and introduction of new technologies on recent immunoanalysis automates. The results observed with the different instruments are similar. Reproductibility has not changed over ten years. Some difficulties remain in the measurement of low concentrations of digoxin. Many substances interfere in digoxin measurement : digoxigenine (inactive metabolite), endogenous digoxin-like immunoreactive factors, spironolacton, antidigoxin antibodies used for treatment of digitalic intoxications. These interferences depend on the method which is used, but it is essential to know them in order to interpret the results correctly.

French experience of quality assessment of quantitative urinary analysis.

Since 1986, clinical biochemists from the Rhône alpes area, in collaboration with a non-profit-making association (Pro Bio Qual), have been conducting an inter-laboratory quality assurance program for quantitative urine analysis. We investigated the precision and accuracy of individual methods and measurement systems routinely used in the monthly control for 13 analytes: albumin, alpha-amylase, calcium, chloride, creatinine, glucose, magnesium, phosphorus, potassium, total protein, sodium, urea, and urate. The number of laboratories participating in the program increased from 60 in 1986 to 277 in 1999. In 1986, the greatest inter-laboratory imprecision occurred in the assay of urinary total protein, because the commonly used sulfosalicylic acid turbidimetric methods displayed poor precision. Since 1989, the increasing use of pyrogallol red or Coomasie Blue dye colorimetric methods has improved inter-laboratory precision markedly. The acceptable precision and good practicability have encouraged the general use of the pyrogallol red method. As for albumin analysis, which uses a specific immunologic method, the precision was reasonably good. Quality assessment of chloride and sodium decreased when the method performance improved for other analytes (calcium, creatinine, glucose, magnesium, phosphorus, potassium, urea, urate). This program has helped the laboratories to improve the quality of quantitative urine analysis, particularly for total protein.