Laboratory samples deemed ‘unsuitable for analysis’ can be diagnostically useful

One percent of laboratory samples are rejected as 'unsuitable for analysis'. Although this may be due to incorrect handling, a proportion are attributable to underlying pathology affecting serum, contamination or artefact. In this Lesson of the month we present two case reports. The first is an obese young man with poorly controlled type 2 diabetes mellitus who presented with acute abdominal pain. Initial blood results were not processed as the automated analyser returned an 'unsuitable' report. The second is an elderly man who presented with abdominal pain and lethargy. He had profound macrocytic anaemia and initial blood results were again deemed 'unsuitable'. In both cases, the laboratory comments had important diagnostic implications. Early identification of lipaemic serum from hypertriglyceridaemic pancreatitis in the first case allowed directed therapy with insulin, and hyperviscous serum from lymphoma in the second allowed directed therapy with plasma exchange and chemotherapy. Other causes of analyser artefact are tabulated to serve as a useful template for hospital doctors in considering underlying causes and practical solutions.