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Related Concept Videos

Urine Studies I: Urinalysis01:29

Urine Studies I: Urinalysis

Urinalysis is a widely used diagnostic test that analyzes urine's physical, chemical, and microscopic characteristics. Healthcare providers use it to detect and monitor various health conditions, including renal disease, urinary tract infections (UTIs), diabetes, and metabolic or systemic disorders.Components of UrinalysisUrinalysis consists of three primary components: physical, chemical, and microscopic examination. Each provides unique insights into the urine sample and, by extension, the...
Unusual Results01:16

Unusual Results

Unusual results are those that have a very low chance of occurring. Unusual results can be identified using probabilities and the range rule of thumb. In problems involving probability, unusual results can be observed in 2 instances – an unusually high number of successes or an unusually low number of successes.
According to the range rule of thumb, any value above or below two standard deviations, 2σ  from the mean, μ  is considered unusual.
Maximum unusual value = μ + 2σ
Minimum unusual value...

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Fecal Glucocorticoid Analysis: Non-invasive Adrenal Monitoring in Equids
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Unusual observations during steroid analysis.

Wai Him Kwok1, David K K Leung, Gary N W Leung

  • 1Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N.T., Hong Kong, China. wh.kwok@hkjc.org.hk

Rapid Communications in Mass Spectrometry : RCM
|February 6, 2008
PubMed
Summary

Steroid screening can produce false positives due to artefacts from internal standards, specifically [16,16,17-d3]-testosterone and [16,16,17-d3]-5alpha-androstane-3alpha,17beta-diol. This highlights potential issues in qualitative confirmatory analyses.

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Area of Science:

  • * Analytical Chemistry
  • * Forensic Toxicology
  • * Biochemistry

Background:

  • * A standard steroid screen of a post-race urine sample revealed 4-androstene-3,17-dione and androsterone.
  • * Confirmatory gas chromatography/mass spectrometry (GC/MS) analyses failed to detect these compounds in the same sample.
  • * Contradictory results between screening and confirmatory methods prompted further investigation.

Purpose of the Study:

  • * To investigate the cause of contradictory findings between steroid screening and GC/MS confirmatory analyses.
  • * To identify the source of detected 4-androstene-3,17-dione and androsterone in a urine sample.
  • * To assess the reliability of internal standards in qualitative confirmatory steroid analysis.

Main Methods:

  • * Initial steroid screening of urine samples.
  • * Gas chromatography/mass spectrometry (GC/MS) analysis for confirmation.
  • * Investigation of potential artefact formation from deuterated internal standards: [16,16,17-d3]-testosterone and [16,16,17-d3]-5alpha-androstane-3alpha,17beta-diol.

Main Results:

  • * Screening detected 4-androstene-3,17-dione and androsterone in one urine sample, but GC/MS did not confirm their presence.
  • * The detected steroids were identified as artefacts originating from the deuterated internal standards used.
  • * Artefact formation was attributed to enzymatic oxidation and deuterium-hydrogen exchange during sample processing.

Conclusions:

  • * The study identified artefacts from specific internal standards ([16,16,17-d3]-testosterone and [16,16,17-d3]-5alpha-androstane-3alpha,17beta-diol) as the cause of false positive steroid screening results.
  • * This highlights a potential problem with using internal standards in qualitative confirmatory analyses, which can lead to false positives.
  • * Careful selection and validation of internal standards are crucial to ensure the accuracy of analytical results in forensic and doping control contexts.