A study of error rates in laboratory medicine

As with any aspect of healthcare, laboratory testing is prone to errors that may have a negative impact on outcome for patients. The focus for laboratory management in this regard has not unnaturally been the analytical process with great emphasis placed on the value of internal and external quality control programs to minimize analytical errors. 

The process of patient testing is, however, much more than the analytic step and significant errors can occur during the preanalytical phase before samples reach the laboratory as well as during the postanalytical phase of reporting and interpreting test results. A recently published Italian study sought to identify and quantify the current error rates for the full process of laboratory testing conducted at the STAT laboratory of a large Italian university teaching hospital. 

For a 3-month study period medical and nursing staff paid particularly careful attention to all test results, recording any questionable results along with pertinent clinical information in the specially designed study notebook that each had been provided. Every day a laboratory physician visited each medical department and investigated every suspected error. 

From a total of 51,746 analyses performed during the study period, clinicians identified 393 questionable results, 160 of which were confirmed as errors, a frequency of 0.309 %. Investigation of the causes of the errors revealed that 61.9 % were preanalytical, 15 % analytical and 23.1 % postanalytical. 

Fourteen different causes of preanalytical error were identified, the most common being tube filling and patient identification errors. This paper provides a comprehensive account of the nature of the errors that can occur in laboratory testing and, more importantly, a model for identifying the error rate that can be used to monitor those rates over time. 

By comparing results of this study with an identical one conducted 10 years ago, the authors were able to demonstrate that improved practice has led to a significant reduction in error frequency from 0.470 % in 1996 to 0.309 % in 2006.