How do I interpret abnormal lab results?

From the Guidelines

When interpreting abnormal lab results, it is crucial to consult with a healthcare provider who can provide context for the specific situation, as they do not always indicate a serious problem. The interpretation of abnormal lab results should be done in the context of the patient's medical history, current medications, and symptoms 1. Abnormal results are those that fall outside the laboratory's reference range, but the degree of abnormality is also important, with slight deviations potentially being less concerning than significant ones.

Key Considerations

• The clinical context is vital, as the same abnormal result can have different implications in different patients 1.
• Trends over time are often more meaningful than single readings.
• Common abnormal results include elevated blood glucose, abnormal cholesterol levels, or abnormal liver enzymes.
• Reference ranges can vary between laboratories and may be adjusted for factors like age, sex, and race.

Recommendations for Abnormal Liver Blood Tests

• Initial investigation should include bilirubin, albumin, alanine aminotransferase (ALT), alkaline phosphatase (ALP), and γ-glutamyltransferase (GGT), along with a full blood count if not already performed within the previous 12 months 1.
• Abnormal liver blood test results should only be interpreted after review of the previous results, past medical history, and current medical condition.
• 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.

Importance of Clinical Context

The interpretation of abnormal liver chemistries must be taken in the clinical context of a given patient 1. This includes an assessment of the patient’s risk factors for liver disease, medications, alcohol consumption, comorbid conditions, and signs and symptoms of hepatic disease. The algorithm approach is useful mainly when there are no clinical clues or when the suspected diagnosis cannot be verified.

Next Steps

• Consult with a healthcare provider to understand the implications of abnormal lab results in the context of the patient's overall health.
• Consider the need for repeat testing or further diagnostic evaluation based on the clinical scenario and the degree of abnormality.
• Never adjust medications or treatments based solely on lab results without professional guidance, as misinterpretation could lead to inappropriate self-treatment 1.

From the FDA Drug Label

The MIC values should be interpreted according to the following criteria: For testing aerobic microorganisms other than Haemophilus influenzae , Haemophilus parainfluenzae, and Neisseria gonorrhoeaea: MIC (μg/mL)Interpretation ≤ 1 Susceptible (S) 2 Intermediate (I) ≥ 4 Resistant (R)

To interpret abnormal lab results, you need to understand the MIC (Minimum Inhibitory Concentration) values and the corresponding interpretation.

• Susceptible (S): The pathogen is likely to be inhibited if the antimicrobial compound in the blood reaches the concentrations usually achievable.
• Intermediate (I): The result should be considered equivocal, and, if the microorganism is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated.
• Resistant (R): The pathogen is not likely to be inhibited if the antimicrobial compound in the blood reaches the concentrations usually achievable; other therapy should be selected. The lab results should be interpreted based on the specific microorganism being tested and the test method used, such as broth microdilution or disk diffusion 2. Key points to consider when interpreting lab results:
• MIC values: Compare the MIC value to the interpretive criteria to determine if the microorganism is susceptible, intermediate, or resistant.
• Test method: Ensure that the test method used is appropriate for the microorganism being tested.
• Quality control: Verify that the laboratory has performed quality control tests to ensure the accuracy of the results.

From the Research

Interpreting Abnormal Lab Results

To interpret abnormal lab results, it is essential to consider several factors, including:

• The reference range for the specific test, as noted in 3
• The patient's medical history and current symptoms, as discussed in 4 and 5
• The potential for laboratory-associated and diagnostic errors, as highlighted in 6
• The need for clear communication of lab results to patients and families, as emphasized in 7

Factors Affecting Lab Results

Several factors can affect lab results, including:

• Analytical uncertainty, as discussed in 3
• Pre- and post-analytical phases of the testing cycle, as mentioned in 6
• Patient conditions and handling of specimens, as noted in 3
• Systematic error and analytical variation, as highlighted in 3

Communicating Lab Results

Effective communication of lab results is crucial, and can be achieved by:

• Providing a clear takeaway message for each result, as recommended in 7
• Signaling whether differences are meaningful or not, as suggested in 7
• Providing thresholds for concern and action, as recommended in 7
• Individualizing the frame of reference by allowing custom reference ranges, as proposed in 7

Clinical Considerations

Clinicians should be aware of the potential for lab results to be incorrect or misleading, and should:

• Evaluate the possibility of laboratory-associated and diagnostic errors, as discussed in 6
• Consider the patient's medical history and current symptoms when interpreting lab results, as noted in 4 and 5
• Use lab results in conjunction with physical assessment findings to inform nursing care, as emphasized in 5