Originally posted April 21st, 2006
To:
Those who will influence the future quality of laboratory testing
CLSI Area Committee on Evaluation Protocols
CLSI Subcommittee on Establishment of Manufacturer’s QC Recommendations
CLSI Subcommitee on Laboratory Quality Control Procedures
I
want to call your attention to an article on “The Quality of Laboratory
Testing Today” that was published in the American Journal of Clinical
Pathology in March 2006 (v125:pp343-354). This article was prepared for
the “QC for the Future” workshop, which was held in March 2005 in
Baltimore. Because you attended this conference and/or are involved in
the ongoing project work to develop QC for the Future, I hope you will
have some interest in the results of this study.
I take the
unusual step of calling your attention to this study to ensure that the
CLSI committees charged with the responsibility for future QC practices
are challenged to consider the current analytical quality of laboratory
tests in quantitative and measurable terms. Emerging laboratory quality
indicators, such as being proposed by IQLM, focus mainly on
pre-analytic and post-analytic variables and pay little attention to
analytical quality. The results of this study indicate that the
analytical quality of laboratory tests is still a serious problem that
requires ongoing improvements in analytical methodology and laboratory
QC.
In considering QC for the
Future, CLSI seems to be driven by the ISO guideline for manufacturers
(ISO 15198: Validation of manufacturer’s recommended procedures for
quality control) which recommends a risk analysis approach to identify
sources of variability that ideally should be eliminated by careful
design of the analytic system. In Section 4 on “Quality control
recommendations,” the following guidance is given to manufacturers:
-
Section 4.1: “Residual risks should be
minimized by the manufacturers’ recommended quality control procedures.
The quality control procedures shall include a method of detection
(e.g., quality control material, electronic monitoring system, or
on-board chemical control) and acceptability criteria that will
determine when a critical failure occurs or a means to determine the
acceptability criteria. Limitations of the quality control procedure
shall be identified and described in the instructions for use.”
While that guidance is fine and
good for manufacturers, I want to remind you of ISO 15189 document
(Medical laboratories – Particular requirements for quality and
competence), which provides guidance to laboratories. In discussing
examination procedures (i.e., measurement procedures), laboratories are
given the following specific guidance:
-
Section 5.5.4: “Performance
specifications for each procedure used in an examination shall relate
to the intended use of that procedure.”
-
Section 5.6.1: “The laboratory shall
design internal quality control systems that verify the attainment of
the intended quality of results.”
Note first the need to define
the “intended use” or “intended quality” in order to implement
examination procedures with appropriate precisian and accuracy, as well
as the appropriate QC design.
Note
first the need to define the “intended use” or “intended quality” in
order to implement examination procedures with appropriate precision
and accuracy, as well as the appropriate QC design. Second, the
guidance for internal QC design doesn’t say mitigate or reduce or minimize the risk of not attaining the intended quality of results - it says to verify the attainment of the intended quality of results.
The laboratory is responsible for verifying that the intended quality
is achieved, not just minimizing the risk of poor quality.
This
objective of verifying the attainment of intended quality of results
can be achieved by designing a statistical QC procedure to account for
the quality required for the test and the precision and accuracy
observed for the measurement procedure, as described in CLSI document
C24-A3 (Statistical Quality Control for Quantitative Measurement
Procedures: Principles and Definitions). Note that the ISO guidance to
manufacturers identifies statistical QC as an example “method of
detection,” thus statistical QC is an appropriate way to monitor
residual risks, as well as to verify the attainment of the intended
quality of test results.
As you develop recommendations
for QC for the Future, please keep in mind that statistical QC is still
a valuable tool to verify the attainment of the intended quality of
test results. There seems to be a predisposition today to try to avoid
the application of statistical QC in laboratories, or reduce the amount
of QC performed, as evidenced by the original CMS proposal for
“equivalent QC procedures.” It is important to set the objective as
performing the right amount of QC to detect medically important errors,
which depend on the quality required for the test and the precision and
accuracy observed for the measurement procedure. In any approach you
recommend, make sure you can account for intended quality and verify
its attainment in routine laboratory operations. Otherwise, we run the
risk that the quality of laboratory testing in the future will be worse
than it is today.
Reference: Westgard JO, Westgard SA. The Quality of Laboratory Testing Today: An assessment of Sigma
metrics for analytic quality using performance data from proficiency
testing surveys and the CLIA criteria for acceptable performance. Am J
Clin Pathol 2006;125:343-354.
We
invite your comments on this open letter. (Please note that we will
moderate all submissions to ensure that commentary is substantive).
