From the Guidelines
Abnormal liver blood test results should be interpreted in the context of the patient's past medical history, current medical condition, and previous test results, and a liver aetiology screen should be considered irrespective of the level and duration of abnormality. When evaluating abnormal liver blood tests, it is essential to consider the extent of liver blood test abnormality, which is not necessarily a guide to clinical significance, as determined by the specific analyte that is abnormal and the clinical context 1. The 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.
Key considerations in the interpretation of abnormal liver blood tests include:
- Review of previous results and past medical history
- Clinical context, including current medical condition
- Extent of liver blood test abnormality, which may not correlate with clinical significance
- Specific analytes that are abnormal, such as ALT, ALP, or GGT
- Need for a liver aetiology screen, including abdominal ultrasound scan, hepatitis B and C testing, and autoantibody panel 1
In adults, a standard liver aetiology screen should include abdominal ultrasound scan, hepatitis B surface antigen, hepatitis C antibody, anti-mitochondrial antibody, anti-smooth muscle antibody, antinuclear antibody, serum immunoglobulins, simultaneous serum ferritin, and transferrin saturation 1. For patients with non-alcoholic fatty liver disease (NAFLD), risk stratification to determine the extent of liver fibrosis is crucial, using either fibrosis-4 (FIB-4) or NAFLD Fibrosis Score (NFS) as first-line testing 1.
From the Research
AGAP on Lab Results
- The anion gap (AGAP) is a calculation used to identify errors in electrolyte measurement and detect paraproteins, as well as evaluate patients with suspected acid-base disorders 2.
- A study published in 2022 compared measurement uncertainty (MU) calculations to real patient result variation observed by physicians using AGAP as a model, and proposed an approach for discretely quantifying pre-analytical contributions and validating AGAP MU estimates for interpretation of patient results 3.
- The study found that MU-derived reference change values (RCV) for paired specimen data by two different platforms was 5.2-6.1 mmol/L assuming no correlation and 2.6-3.1 mmol/L assuming correlation, and that total observed variation on a reported AGAP has a 95% confidence interval of ±6.0 mmol/L 3.
- Another study published in 2023 reviewed the constituents of the anion gap and provided a stepwise approach to diagnostic testing to evaluate a low anion gap, highlighting the importance of considering this abnormal finding in clinical practice 4.
- The calculation of the serum anion gap has limitations, including a wide range of normal values and the effect of perturbations other than changes in acid-base balance, and its effectiveness in identifying mild and more severe disturbances in acid-base balance is limited 2.
Laboratory Diagnosis
- The laboratory diagnosis of iron deficiency anemia (IDA) involves measuring serum iron, transferrin saturation, ferritin, and hepcidin levels, as well as total iron binding capacity and soluble transferrin receptors 5.
- A study published in 2019 compared the effects of ferrous sulfate and Illicium verum on liver function in a rat model of iron-deficiency anemia, and found that Illicium verum produced similar effects to ferrous sulfate without affecting liver function 6.
- Iron metabolism and homeostasis play a crucial role in the development of IDA, and understanding these processes is essential for accurate diagnosis and management 5.