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Understanding variability in biomarker testing with Igloo Reader Pro.

Biomarker testing - whether for hormones, vitamins, inflammation markers, or other health indicators - is subject to natural variability. Differences can arise between various measurement methods, and even repeated tests on the same device can show some variation. This is a normal part of biological testing due to multiple influencing factors.

Many elements impact test results when using point-of-care devices like the Igloo Reader Pro. These include technical factors related to the device and assay, as well as human-dependent factors such as sample collection and handling. Similar challenges also exist in traditional clinical laboratory testing, where variables like sample storage, transport time, and environmental exposure can affect outcomes.

Regulatory guidelines acknowledge this variability by defining acceptable tolerance ranges for different biomarkers, ensuring that small deviations are not mistaken for errors but are recognized as normal fluctuations.

Factors affecting biomarker measurement accuracy

A variety of factors can influence the accuracy and consistency of biomarker test results. Some variations come from natural biological fluctuations within the patient, while others arise from how samples are collected and handled or how the assay detects the biomarker. These factors include but not limited to:

  • Biological variability: Biomarker levels can fluctuate naturally based on age, gender, time of day, recent food intake, and other physiological factors.
  • Sample collection: Proper technique is crucial - improper handling, insufficient sample volume, or contamination can skew results.
  • Sample storage and transport: Exposure to extreme temperatures, light, or prolonged transport times can degrade samples or affect biomarker stability.
  • Assay specificity: Different tests may target different forms or isoforms of a biomarker, which may not be directly comparable.
  • Measurement units: Biomarker levels may be reported in different units, requiring conversions to interpret correctly.
  • Medication and lifestyle: Drugs, supplements, and lifestyle choices (like alcohol or caffeine intake) can alter biomarker concentrations.

Acceptable analytical variability for selected biomarkers

To support consistent interpretation of biomarker results, regulatory frameworks define acceptable ranges of analytical variation. These ranges account for biological variability, assay performance, and methodological differences, and help distinguish normal measurement fluctuation from true analytical error.

According to the German Rili-BÄK quality assurance guidelines (status: 14 April 2023), the following permissible deviations are considered acceptable for selected analytes:

  • Vitamin D (25-hydroxyvitamin D): ±25%
  • HbA1c: ±3%
  • C-reactive protein (CRP): ±13.5%
  • Thyroid-stimulating hormone (TSH): ±13.5%
  • Ferritin: ±13.5%

Results that fall within these tolerance ranges are regarded as analytically reliable and compliant with established quality standards. When comparing results across different testing methods or over time, these allowable deviations should be taken into account to avoid misinterpretation.

Best practices for reliable point-of-care biomarker testing

Ensuring the highest accuracy in point-of-care biomarker testing requires attention to detail during sample collection and processing. Following best practices minimizes errors and improves reliability. When using the Igloo Reader Pro, it is important to:

  • Allow disinfectants to dry fully before sample collection to avoid contamination.
  • Discard the first drop of blood during fingerstick sampling to avoid tissue fluid interference; use only the subsequent drop.
  • Avoid excessive squeezing or massaging of the finger, which can dilute the sample.
  • Collect the correct volume of sample as specified by the test instructions.
  • Adhere strictly to the incubation times and handling procedures outlined by the test manufacturer.

Vitamin D testing: A detailed example

Vitamin D testing highlights many of the complexities and considerations relevant to biomarker measurement. Understanding these specifics helps interpret results accurately and manage patient care effectively. Key points include:

  • Different forms measured: Different laboratories may test for the storage form (25-hydroxyvitamin D or 25(OH)D) or the active form (1,25-dihydroxyvitamin D). These represent different physiological states and their results are not interchangeable.

  • Units and conversion: The Igloo test report specifies ng/mL (nanograms per millilitre), while many laboratories measure in nmol/L (nanomoles per litre). A reference table can also be found in the test instructions. The standard conversions are:

    • 1 ng/mL = 2.5 nmol/L

    • 1 nmol/L = 0.4 ng/mL

  • Regulatory tolerance: Guidelines such as the German Rili-BÄK allow a ±25% variation in Vitamin D results to accommodate normal assay and biological variability.

  • Influencing factors: Vitamin D levels can be affected by obesity (due to storage in fat tissue), recent supplementation, sun exposure, and certain medications (e.g., corticosteroids, immunosuppressants).

  • Sample handling: Exposure of the sample to light or improper storage conditions can degrade Vitamin D, affecting test accuracy.

  • Example: A customer effectively has a value of 40 ng/mL, and two different measurements are taken. One method yields a value of 50 ng/mL, and another method reports a value of 30 ng/mL. Although these appear quite different, both fall within the allowed ± 25% tolerance range and are therefore considered accurate.

Summary

Understanding the general principles of biomarker measurement helps ensure accurate interpretation and reliable testing outcomes. Biological variability, sample handling, assay design, and methodological differences all contribute to expected result variation across testing platforms.

When combined with correct sample collection and adherence to test instructions, the Igloo Reader Pro provides consistent, high-quality point-of-care results across a wide range of biomarkers. This enables confident decision-making and meaningful health insights directly at the point of care.

Disclaimer

This information is provided for educational and informational purposes only and is not intended to replace professional medical advice, diagnosis, or treatment. Biomarker results should always be interpreted in the context of clinical findings, patient history, and applicable guidelines with qualified healthcare professionals. When required, confirmatory testing using standardized laboratory methods is recommended. Always follow the instructions for use (IFU) provided with each test.