Endocrine Abstracts (2009) 19 S46

What service does the laboratory provide?

Julian Barth

Leeds General Infirmary, Leeds, UK.

Advances in instrument technology and automation have simplified tasks in laboratory diagnostics and improved the quality of test results. However, errors occurring during the preanalytical phase – from the time the test is ordered by the physician until the sample is ready for analysis – can account for up to 93% of the errors currently encountered during the total diagnostic process.

The precision of analytical problems has been significantly improved over the past decades but has been replaced by the problem of standardisation with (often) considerable variation between methods which is sufficient to change clinical management if data are misinterpreted. Additional potential error can be introduced by ignoring the units in which results are reported. Both these factors become an issue if interpretation is based purely on published data from other laboratories. A source of error in laboratory analyses is due to interference by endogenous antibodies. These are not identified by routine quality checks. There are several strategies to uncover these errors but since they can only be revealed by interpretation with the clinical picture, it is essential to maintain close liaison with the laboratory scientists.

Most assays are standardised on random samples, whereas many endocrine investigations often employ stimulation tests. The effect of stimulation results in reduced assay specificity due to the presence in serum of precursor hormones or by the alteration in the pattern of hormones due to differential clearance. There is only little data on these effects and, moreover, the data rapidly becomes invalid due to changed assay architecture.

There are many aspects of the laboratory service in the pre-analytical, analytical and post-analytical phases that can lead to mismanagement. Prevention requires good communication between laboratory and clinical scientists.

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