From the Guidelines
When interpreting abnormal lab results, it is crucial to consult with a healthcare provider who can provide context and guidance specific to the individual's situation, as abnormal results do not always indicate a serious problem. The interpretation of abnormal liver chemistry tests must be taken in the clinical context of a given patient 1. This involves a detailed history, inventory of medications, and a physical examination to assess the patient’s risk factors for liver disease, medications, alcohol consumption, comorbid conditions, and signs and symptoms of hepatic disease.
Key factors to consider when interpreting abnormal lab results include:
- The degree of abnormality, with slight deviations potentially being less concerning than dramatic ones
- The patient's medical history, current medications, and symptoms
- The need for repeat testing to confirm findings, especially if the abnormality is unexpected
- Tracking results over time, as trends are often more meaningful than single readings
- Common factors that can affect lab results, such as fasting status, hydration, medications, time of day, and recent physical activity
According to the guidelines on the management of abnormal liver blood tests, abnormal liver blood test results should only be interpreted after review of the previous results, past medical history, and current medical condition 1. The extent of liver blood test abnormality is not necessarily a guide to clinical significance, which is determined by the specific analyte that is abnormal and the clinical context 1.
Initial investigation for potential liver disease should include bilirubin, albumin, alanine aminotransferase (ALT), alkaline phosphatase (ALP), and γ-glutamyltransferase (GGT), together with a full blood count if not already performed within the previous 12 months 1. Patients with abnormal liver blood tests should be considered for investigation with a liver aetiology screen, irrespective of the level and duration of abnormality 1.
Ultimately, understanding the clinical significance of abnormal results requires medical expertise, so while it's good to be informed, interpretation should ultimately be done with professional guidance.
From the Research
Interpreting Abnormal Lab Results
To interpret abnormal lab results, it is essential to consider the context in which the tests were performed, as well as the reference intervals provided by the laboratory 2. The following points should be taken into account:
- Contextual tests: These tests require a physiological condition to correctly interpret the result. For example, thyroid function tests should be interpreted in the context of the patient's clinical presentation and medical history 3.
- Reference intervals: These intervals describe the population from which they were determined and may have utility in this regard. However, it is essential to consider the cultural, biological, physiological, and behavioral diversity of the population sampled to determine normality 2.
- Pitfalls and caveats: When interpreting lab results, it is crucial to be aware of possible assay interferences and/or the effects of concurrent medications. Additionally, thyroid function may appear abnormal in the absence of actual thyroid dysfunction during pregnancy and in critical illness 3.
- Clinical utility: Laboratory tests should be used in conjunction with clinical judgment to diagnose and manage diseases. For example, blood tests for thyroid-stimulating hormone (TSH), free thyroxine, and free triiodothyronine are frequently used to assess the functional status of the thyroid 3.
Common Lab Tests and Their Interpretation
Some common lab tests and their interpretation include:
- Thyroid function tests: TSH and free thyroid hormone tests are used to assess the functional status of the thyroid. TPO-Ab and TRAb tests are used to diagnose Hashimoto's thyroiditis and Graves' disease, respectively 3.
- Liver function tests: Ursodeoxycholic acid (UDCA) is used in the treatment of cholestatic liver diseases, and its efficacy has been debated. The mechanisms of action of UDCA in humans have not been fully defined 4.
- Cardiac biomarkers: Troponin-T and N-terminal pro-B-type natriuretic peptide (BNP) are used to assess cardiac function. In patients with transthyretin cardiac amyloidosis, these biomarkers may be elevated, and treatment with doxycycline and ursodeoxycholic acid may be associated with stabilized markers of disease progression 5.