Routine blood work is essential for maintaining overall health and preventing diseases. Blood tests provide valuable insights into a person's health status and can help detect potential health issues before they become serious. These reports can identify risk factors for conditions such as diabetes, anaemia, and heart disease. Early detection allows for timely interventions, lifestyle changes, or treatments that can significantly improve health outcomes.

Additionally, routine blood tests help monitor the effectiveness of ongoing treatments and provide information on how well organs, such as the liver and kidneys, are functioning. Regular testing also establishes a baseline for a person's normal levels, making it easier to spot any significant changes over time.

However, it's important to understand that blood test results can vary between laboratories due to several factors.

Blood test results can differ between laboratories without either report being incorrect. Variation can occur at several stages, from how the sample is collected to how it is analysed.

Factors That Contribute to Variation:

1. Sample Collection and Handling

This is the biggest influencer. Factors like fasting status, recent food intake, exercise, hydration, stress, medications, and the time of day can all impact certain parameters. Additionally, delays in transport, improper storage, or hemolysis (destruction of red blood cells) can affect results.

2. Analytical Method

Laboratories use different analysers, reagents, and calibration systems. Well-standardised tests like HbA1c and glucose show minimal variation, while hormone levels, vitamin D, and tumour markers can differ significantly between platforms. Each laboratory also establishes its own reference range, so it's important to evaluate results against that specific lab's range rather than relying on absolute numbers alone.

3. Repeating the Test at Another Lab:

Many people choose to repeat a test at a different laboratory a few days later and become anxious if the numbers differ. This introduces two sources of variation: the body naturally changes over days-hormones, glucose, and lipids fluctuate-and the testing methods may vary as well. A modest difference in results is to be expected.

When Should You Be Concerned?

Most small differences in test results are just noise, which is a measurable statistic. Laboratory medicine uses a statistical threshold (the reference change value); for many tests, a result must shift by roughly 15-30% before it is considered a significant change rather than random fluctuation.

  • Check the Category, Not Just the Numbers: If both reports place you within the same clinical category, the overall message is consistent.
  • Seek Medical Review: Consult your doctor if you see a substantial change from your previous results, a value that falls well outside the reference range, an abnormal result accompanied by symptoms, or critical values such as extremely high or low glucose, potassium, or haemoglobin levels.
  • Never Act on a Single Report: Before making any major decisions, such as beginning lifelong medication, doctors will confirm results with a repeat test under proper conditions.

For monitoring chronic conditions, it's best to conduct tests under similar conditions at the same accredited laboratory. These labs perform daily quality checks to minimise variation. Additionally, it's crucial to consider the context of the results; if a patient experiences symptoms that correspond with abnormal test results, they should seek medical advice promptly. Discussing any results with a healthcare provider can help clarify their meaning and guide the next steps for maintaining health.

(Dr Ajay Phadke, Director, Strategic Business Development, Agilus Diagnostics)



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