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Pereira continues part 2 of a series on the ISO standards applicable to medical laboratories. The ISO is widely popular for laboratories, but many aspects are confusing, vague, and misunderstood.
Unfortunately ISO implementation is frequently accompanied by misunderstandings. Therefore, this essay is intended to discuss some specifications briefly and to debate what is happening with ISO implementation in the world. The standard document is focused on the medical laboratory, and its goals can be interpreted as the satisfaction of interested parties 4 of .
Stakeholders cannot be understood as customers only, such as patients, but inclusive of any internal or external involvement with the medical laboratory, including, but not only, professionals, suppliers and accreditation agencies. For this purpose, this international standard is based not only on a management system but also on a set of medical laboratory technical specifications. Despite the lab sustainability should be controlled, it is not mandatory.
It quickly became a widely-accepted standard to be used for accreditation of medical laboratory competence. When a medical laboratory chooses an accreditation plan, it should select an accrediting body that operates according to appropriate international standards and which takes into account the particular requirements of this field.
The framework provides a quality management system close to the ISO management requirements added by specifications for technical competence that are particular to medical laboratories. The standard quality management model is based on the Deming TQM approach   . Figure 1 displays a quality cycle applicable to a medical laboratory under ISO accreditation. The leadership is critical to the success of all the cycle phases.
This terminology is already revised in the current ISO edition 4. Table 1 summarizes these stipulations. Table 1: Summary of ISO specifications 5. Quality control procedures design to verify the attainment of the intended quality of results, quality control materials, quality control data, interlaboratory comparisons, analysis of interlaboratory comparison samples, evaluation of laboratory performance, and comparability of examination results.
Review of results, storage, retention, and disposal of clinical samples. Reagents and consumables: Documented procedure, reception and storage, acceptance testing, inventory management, instructions for use, adverse incident reporting, and records.
Report of examination results, the report attributes, and content. Documented procedures, automatic selection and reporting of results, and revised reports. Authorities and responsibilities, and information system management. Sub-chapters 5. Preferably, traceable metrological materials should be used.
When these materials are not available, or their use is not significant to the estimate accuracy, alternative materials could be used. See for a more in-depth discussion see . For instance, a screening test selection in a blood bank should assure that a method with high diagnostic sensitivity  is chosen to minimize the residual risk 2. ISO does not recommend any approach to select a new test. Usually, it is based on a literature review using validation cases of state-of-the-art methods.
The verification shall confirm with evidence that the laboratory performance claims have been met. The calculations are based on experimental data.
Therefore, the specifications, such as the allowable total error, allowable diagnostic sensitivity or allowable diagnostic specificity are selected accordingly.
As with verification of non-modified tests, experimental data is involved with validation of modified tests. The methodology is as complex as needed, and it is identical to what is required to the manufacturer in the validation phase. CLSI guidelines referred to in 5. For example, the calculation of a clinical decision point based on representative samples of the population.
For qualitative results, measurement uncertainty cannot be computed. Even if the qualitative results are expressed on an ordinal scale according to cutoff, its determination is optional. ISO does not recommend a methodology to calculate measurement uncertainty.
Empirical models should be used, preferably using data from the validation of the examination procedure phase. Measurement uncertainty is an additional model that is part of the evaluation of the quality of the reported result, which could be applied to any measurement. Target uncertainty must be defined, which can be very complex. See  for further details.
Measurement uncertainty implementation has not been widely successful in medical laboratories, even after 23 years since GUM was published, such as demonstrated by the Westgard QC survey . An alternative to the Levey-Jennings charts could be used, such as the exponentially weighted moving average EWMA chart 9.
Nevertheless, the practical suggestion is to use statistical QC based on the Sigma-metrics  principally because it relates the determined total error with the allowable total error. The allowable total error is equivalent to the error that does not significantly contribute to incorrect clinical decisions. For a depth discussion on this issue, please see .
For instance, when a result is out of acceptable group requirements. There are no specific recommended approaches.
Figure 2 represents the steps from the test selection to the reported results. The accomplishment of the examination and post-examination phases are dependent on the pre-examination stage. Principally two publications: David Burnett, Ph. Which references can support ISO specifications on examination and post-examination activities?