Data on a set of QIs collected over a 3-year time-frame demonstrate that processes and indicators under the control of the clinical laboratory had improved much more than processes requiring close co-operation between the laboratory and care teams.
Laboratory diagnostics is a complex and multifaceted enterprise, developing throughout a multiple series of activities traditionally clustered within fi ve main phases, i.e., the pre-preanalytical, preanalytical, analytical, post-analytical and post-post-analytical. Although remarkable technological advancements, internal quality control, external quality assessment and/or profi ciency testing have enabled to consistently decrease the burden of errors in the central, analytical phase (1 -3) , several problems still plague other activities of the total testing process (4) . Reliable evidence attests that the vast majority of errors in the modern laboratory diagnostics occurs in the preanalytical phase, whereby a series of manually intensive procedures, not appropriately automated or non automatable, make blood collection inherently vulnerable to ambiguity and human faults (5, 6) . Results of several studies and surveys attest that most preanalytical errors are attributable to collection of samples of inappropriate quality (i.e., haemolysed, clotted, contaminated) or quantity (i.e., insuffi cient volume, incorrect blood to anticoagulant ratio). Although these preanalytical mistakes still jeopardise patient ' s safety when the samples are processed with generation of unreliable data, they are however straightforwardly detectable before test results are being released to the clinicians by either visual inspection of the sample or through technological aids such as the use of serum indices (7) . Misidentifi cation is an additional source of errors in the preanalytical phase, which is reportedly less frequent, but potentially much more hazardous. Identifi cation errors virtually affl ict each medical activity, whenever there is a direct interaction between the patient and a healthcare professional, either for diagnostic, clinical or therapeutic purposes.Identifi cation errors might occur with a signifi cant frequency in nearly almost diagnostic disciplines, including laboratory medicine (from approx. 1 % to 9 % of cases) (8) , transfusion medicine (from 0.7 % to 3.2 % ) (9, 10) , anatomic pathology (approx. 1 % ) (11) as well as radiology, where the frequency of incorrect patient data and side markers in a recent survey was found to be unpredictably higher (i.e., 18 % and 5 % of cases, respectively) than in other diagnostic disciplines (12) .
SUMMARY.A group of international experts prepared two lists of drugs with their serum/plasma and urine concentrations, which should be used when evaluating the performance of a new laboratory method. The two lists were veri®ed by running in vitro interference studies in three European laboratories on Hitachi instruments. The study identi®ed the following new interferants: acid phosphatase in serum by ibuprofen and theophylline; non-prostatic acid phosphatase in serum by cefoxitin and doxycycline; creatine kinase MB in serum by doxycycline; total bilirubin in serum (Jendrassik±Grof method) by rifampicin and intralipid; total bilirubin in serum (DPD method) by intralipid; creatinine in serum (Jaffe method) by cefoxitin; fructosamine in serum by levodopa and methyldopa; uric acid in serum by levodopa, methyldopa and tetracycline; carbamazepine in serum by doxycycline, levodopa, methyldopa and metronidazole; digitoxin in serum by rifampcin; phenytoin in serum by doxycycline, ibuprofen, metronidazole and theophylline; theophylline in serum by acetaminophen, cefoxitin, doxycycline, levodopa, phenylbutazone and rifampicin; tobramycin in serum by cefoxitin, doxycycline, levodopa, rifampicin and phenylbutazone; valproic acid in serum by phenylbutazone; C3 in serum by intralipid; C4 in serum by doxycycline; rheumatoid factor in serum by ibuprofen and metronidazole; pancreatic amylase and total amylase in urine by acetylcysteine, ascorbic acid, cefoxitin, gentamicin, levodopa, methyldopa and o¯oxacin; magnesium in urine by acetylcysteine, gentamicin and methyldopa; b 2 -microglobulin in urine by ascorbic acid; total protein in urine by ascorbic acid, Ca-dobesilate and phenylbutazone.Interference in acid phosphatase, creatine kinase MB and bilirubin methods was observed at very low analyte concentrations, and therefore it may not be evident at higher concentrations. The study con®rmed the usefulness of the recommendation.
In response to proposals of scientific associations the German Medical Association recommended the use of international standard procedures for the determination of enzymes and a change of the measurement temperature to 378C in 1992. According to the recommendations, reference intervals for the new reference procedures should have been published by 1995. After a transition period, which had been extended several times, the clinical chemistry laboratories finally had to follow the recommendations and to use the new IFCC reference procedures as of April 1, 2003. However, reference intervals evaluated in a multicentre study have not been published until now. There is only one German study on preliminary upper reference limits of five enzymes in serum of hospitalized subjects using the new IFCC reference procedures. Since no multicentre study is intended in the near future, an expert working group of DGKL and VDGH recommended the use of preliminary reference intervals on enzymes in serum until final values have been determined. The interim values result from experiences of the past 3 years, from previous studies in different countries using comparable methodologies, or were derived from reference intervals obtained at 258C and converted by method and temperature conversion factors. ZusammenfassungAuf Vorschlag wissenschaftlicher Fachgesellschaften hat die Bundesä rztekammer 1992 die Einfü hrung internationaler Standardmethoden zur Bestimmung von Enzymaktivitä ten und damit auch die Umstellung der Messtemperatur von 258C auf 378C beschlossen. Referenzintervalle fü r die neuen Enzymmethoden sollten bis Ende 1995 verö ffentlicht werden. Nach einer mehrmalig verlä ngerten Ü bergangsphase bestand fü r die Laboratorien die Verpflichtung die neuen IFCC-Methoden ab 1.4. 2003 anzuwenden. Referenzbereiche, ermittelt in einer multizentrischen Studie, wurden nicht verö ffentlicht. Bisher liegt nur eine publizierte deutsche Studie vor, bei der lediglich an Krankenhauspatienten fü r fü nf Enzyme die oberen Referenzbereichsgrenzen bei 378C adaptiert an die IFCC-Methoden vergleichend zu den frü heren 258C-Methoden gemessen wurden. Da eine multizentrische deutsche Referenzwertstudie bisher nicht geplant ist, empfiehlt eine Arbeitsgruppe aus Experten der DGKL und des VDGH vorlä ufige obere Referenzbereichsgrenzen, die bis zur Erhebung definitiver Werte in einer multizentrischen Studie Gü ltigkeit haben sollen. Die vorlä ufigen oberen Referenzbereichsgrenzen beruhen auf einer 3-jä hrigen Erfahrung, wurden an frü here internationale Publikationen adaptiert oder von den 258C-Methoden abgeleitet.Schlü sselwö rter: Enzyme; IFCC-Methoden; Referenzbereiche.
ZusammenfassungDie Richtlinie der Bundesärztekammer zur Qualitätssicherung laboratoriums medizinischer Untersuchungen (RiliBÄK) schreibt u. a. auch Ringversuche für die Durchführung von patientennaher Diagnostik (POCT) vor. Bei der Be- und Auswertung dieser Ringversuche ergeben sich Probleme, wie z.B. schlechte Übereinstimmung zur Referenzmethode, Matrixeffekte der Kontrollproben, die dazu führen, dass keine Zertifikate erteilt werden k\xf6nnen. In einer gemeinsamen Stellungnahme wird der derzeitige Stand der Problematik beschrieben. So ist die Auswertung zurzeit nur über das sogenannte Consensus Value Model (Mittelwert aus den eingesandten Resultaten in Abhängigkeit der verwendeten Methode) möglich, da ein geeignetes Probenmaterial für die Kontrollproben nicht zur Verfügung steht. Der Referenzmethodenwert eignet sich auf Grund der Problematik nicht als Zielwert.
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