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Difference Between Urine Analysis And Drug Testing

640px-Urinary_phase-contrast_microscopy

Urinalysis or simply study of urine is the method of screening the urine of a person to detect normal and abnormal constituents. The process is safe and simple as it is a non-invasive technique, and requires only collection of diurnal urine. Further such process is neither associated with any discomfort nor adverse effects. In this analytical procedure, an array of tests is performed on the urine either for medical or legal purposes (illegal drugs used for purpose of performance enhancement)[1].

The tests usually involve evaluation of colour, density, pH and presence or absence of specific biochemical substances or drugs. The common methods of urine analysis are uroscopy (Physical analysis), by reagent strips (chemical reactions with urine components) and microscopic (immunoassays). Urinalysis is often done either for medical conditions or Drug Testing. Drug testing in urine involves the presence of a drug or its metabolite as per its pharmacological profile. Urinalysis provides an avenue towards medical abnormalities or drug overdose and misuse[1].  A brief of medical conditions associated with urine profile is tabulated as below[1,2]:

Urine Parameter Normal Values Deviated values Interpretation
pH 7.4 to 7.6 <4.5
<6.0/6.5>7.6
General acidosis in the bodyDecreased absorption of minerals like Copper, Iron Phosphorus and also important vitamins like A,B,E,F and KTissues unsaturated with vitamin C
Nitrites Negative(not found) Positive(if found)False positive Urinary tract infectionsUsing phenazopyridine as an adjunct to UTI as an analgesic
Leukocytes(white blood cells) Negative(not found) Positive(if found) Presence of bacterial exotoxins or due to an infection called cystitis
Ketone bodies Negative(not found) Positive(if found) Diabetes or starvation
Glucose Negative(not found) Positive(if found) Known as glucosuria and may indicate diabetes.
Bilirubin Negative(not found) Positive(if found) Jaundice, indicating gall bladder dysfunction
Blood Negative, however 100mg/dl is normal >100mg/dl UTI or cancer of the urinary bladder
Proteins Negative(not found) Positive(if found) Known as proteinuria  and indicates glomerulonephritis
Colour Evaluation Colorless BlackBlueBrown, yellow or goldenWhiteRed Kidney infection or genetic disease called Alkaptonuria
Tryptophan malabsorption
Jaundice or dehydration, decreased Vitamin B12 absorptionPyuria or pus cells present
Presence of blood

Apart from these chemical components, and physical characteristics urinalysis serves to detect drugs. Drug testing is performed to evaluate whether drug metabolism is normal, whether a person has been on drug overdose or an individual has consumed drugs for “Doping” purposes. However it can be quite natural that an individual is on a prescribed medication and the drug levels detected is a result of physician prescribed intake[2].

Various factors influence the detection of a drug in one’s urine. The factors include state of hydration of the individual, half life of the drug, dosing frequency, route of administration of the drug. Sometimes to elicit performance enhancement synthetic components which mimic physiological substances are used. Example of these are synthetic steroids, testosterone or erythropoietin which are all considered as illegal drugs if detected in urine and the individual fails to show that it is a physician prescribed administration. The advantage and disadvantage of drug testing is narrated as in Table 1[2].

Advantage Disadvantage
  1. Non-Invasive
  2. Drug and its metabolites are stable, and is present in effective concentrations for detection
  3. Rapidly preserved by freezing
  1. Influenced by voiding pattern, fluid intake
  2. Might not correlate with physiological levels
  3. May provide faulty values if not preserved properly.

The following table (Table 2) provides the summary of such drugs being tested for presence in urine[2,3].

Drug Class Cut Off Limits (ng/dl) Used For Detected in Urine
Amphetamines 1000 Euphoria, stimulant Till 2 days of intake
Barbiturates 200 As antidepressants, sedatives Till 2 days to 3 weeks depending on half life
Benzodiazepines 200 Sedatives Till 3 days (therapeutic dose)or 4 weeks( chronic intake)
Cocaine 300 stimulant Till 4 days
codeine 300 analgesic Till 2 days
Cannibinoids like marijuana 100 hallucinogen 2-7 days (if used as a single dose) while 1 to 2 months in case of prolonged use.

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References :


[0]Hardman JG, Limbird LE, eds. Goodman and Gilman’s pharmacological basis of therapeutics. 10th ed. New York: McGraw Hill. 2001:621

[1]Urine drug testing in the clinical laboratory: Approved guideline. Wayne, PA: National Committee for Clinical Laboratory Standards (Document T/DM8-A, Vol. 19, No. 6), 1999.

[2]Braithwaite RA, Jarvie DR, Minty PS, et al. Screening for drugs of abuse. Opiates, amphetamines and cocaine. Ann Clin Biochem. 1995;32:123-153.

[3]http://en.wikipedia.org/wiki/Urinalysis

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