49
Materiales de referencia y comparaciones interlaboratorios
tion of the test. Morris and Macey (2004) demonstrated that accredited laboratories perform
better in the CAEAL PT program than non-accredited laboratories. Although their evaluation
was limited to two studies and five parameters,the data suggested that there was an improve-
ment in average laboratory performance from one study to the next (1997 and 2001), regard-
less of the labs’ accreditation status.The current study substantiates this observation.
This study clearly demonstrates that, on average, there is an improvement in analytical quality
over the first few rounds of PT participation. It could be argued that, since PT participation is
usually part of an overall quality assurance program, the observed improvement is the result
of a combination of efforts, not proficiency testing alone. Although this is certainly true at
some level, most other QA related factors would affect all tests in a laboratory concurrently,
whereas the design of the current study is such that time zero spans a duration of five years
(1995 – 1999).This suggests that the observed trend can be largely attributed to PT participa-
tion.
Similar observations have been made for PT participation in the clinical laboratory industry.
Taylor and Fulford (1981), using PT performance as a measure, observed that many clini-
cal tests demonstrated an improvement in performance over time and some showed little
change. Hassemer [7] examined clinical PT performance from 1993 to 1996 (11 PT rounds).
He observed that the percentage of labs with acceptable scores dropped in 1994, due to the
influx of a large number of newly participating laboratories (PT participation became manda-
tory in 1994), followed by a gradual improvement during the next few rounds. These studies
further support the conclusion that PT participation has a direct positive impact on laboratory
performance.
Laboratory accreditation and proficiency testing are a powerful combination, providing the
tools necessary to effectively manage a laboratory. Conformance to ISO/IEC 17025 (through
accreditation) ensures that a laboratory has effective management tools in place. Proficiency
testing allows a laboratory to monitor performance, providing a feedback mechanism for
identifying areas of concern for investigation and corrective actions.
V. References
[1] ISO/IEC Guide 43-1:1997 “Proficiency testing by interlaboratory comparisons- Part 1: De-
velopment and operation of proficiency testing schemes”and ISO/IEC Guide 43-2:1997“P
roficiency testing by interlaboratory comparisons- Part 2: Selection and use of proficiency
testing schemes by laboratory accreditation bodies”.
[2] ILAC-G13:2000 Guidelines for the Requirements for the Competence of Providers of. Profi-
ciency Testing Schemes.
[3] CAN-P-1593. January 2001. ã2001 – Standards Council of Canada. “Conditions for the Rec-
ognition of Proficiency Testing Schemes”
[4] Morris, A. and D. Macey. 2004. Laboratory accreditation: Proof of prformance for environ-
mental laboratories-2001 study. Accred. Qual. Assur. 9:52-54.
[5] ISO/IEC 17025:2005.“General requirements for the competence of testing and calibration
laboratories”
[6] CAN-P-4D - General requirements for the competence of testing and calibration laborato-
ries
[7] Hassemer, D. 1996. Does proficiency testing help labs improve? In a word, Yes. Wisconsin
State Laboratory of Hygiene, newsletter # 10.
[8] Taylor, R. N. and K. M. Fulford. 1981. Assessment of laboratory improvement by the centre
for disease control diagnostic immunology proficiency testing program. J. Clin. Microbiol.
13:356-368.
