Laboratory tests are essential for establishing diagnosis and prognosis, monitoring disease progression and making treatment decisions. Interpretation of laboratory results requires an understanding of the potential limitation of the test combined with the clinical context of why the test was ordered and the patient’s overall clinical picture.¹ Incorrect results can occur due to errors during sample collection or interpretation, which can lead to missed diagnoses or unnecessary treatments.²These factors need to be borne in mind when interpreting laboratory test results.

The State Claims Agency identified 28 incidents relating to interpreting laboratory tests over a six-month period. Some examples included:

• Incorrect results issued, resulting in, or having the potential to result in, diagnostic errors affecting the care and management of service users. These occurred when conflicting verbal and written results were issued by laboratories (e.g. incorrect verbal report of low blood sodium level) or when confirmatory tests were not carried out prior to issuing of results
• False negative results, due to defective laboratory assay, with the potential to impact treatment options
• Transcriptional errors in reports, when a result was selected that was similar by spelling (e.g. ‘staph SPP’ selected instead of ‘streptococcus SPP’) or when a negative instead of positive result was selected
• Incorrect diagnosis based on the failure to appreciate test sensitivity and specificity. These incidents occurred in circumstances where a diagnosis was not based on superior ‘gold standard’ tests
• Misinterpretation of test results, when the test requestor/treating clinical personnel misinterpreted or mistook the test result, particularly complex results, in some cases resulting in incorrect management of the service user

The small number of incidents reported may suggest an element of under-reporting and that further opportunities for learning and improvement are potentially being missed. In general incident reporting is seen as contributing to a positive patient safety culture and is a fundamental component of good risk management.

Minimising the risks

In order to mitigate the risk of patients being impacted by issues related to laboratory testing, it is advised that clinical personnel involved in requesting or interpreting laboratory results should:

• Be alert to inconsistent or conflicting laboratory results, seeking clarification and confirmation of the results where necessary
• Ensure, where a confirmatory or supplementary result is required, that these results are received and reviewed; until then, results should be considered preliminary
• Ensure test results are consistent with the clinical picture and test request, as well as with the results of any additional tests performed (past and present). Treat the patient, not the test result
• Understand the sensitivity and specificity of initial testing and request more sensitive or specific testing when indicated
• Seek advice in interpreting complex test results
• Report incidents as soon as possible to the National Incident Management System (NIMS), so that learning can occur

References available on request.