specimen collection
18
ADULTERATION & DILUTION DETECTION
Means to detect adulteration by the collector and/or the laboratory
include the following:
1. Specimen Temperature: If specimen collection is not
witnessed, the most effective means to detect specimen dilu-
tion, adulteration, or substitution is to measure the sample’s
temperature. The collector should measure the temperature
utilizing the temperature strip afxed to the specimen con-
tainer within four minutes of collection; it should read between
90 and 100 degrees Fahrenheit. The urine temperature should
be noted on Urine Test Request form.
2. Urine Appearance and Odor: Adulterants such as isopro-
pyl alcohol, soaps, bleach and perfumes are readily identied
by their odor. Soaps are also identied by excessive bubbling.
Use of solid adulterants is detected by the presence of residues
in the container.
3. Creatinine: In general, creatinine is a metabolic byproduct
of muscle metabolism which normally appears in urine in rela-
tively constant quantities over each 24 hour period. Therefore,
urine creatinine can be used both as a marker to specically
identify a specimen as urine, and as an indicator of urine water
content (dilution). “Normal” random urine specimens will
generally have urine creatinine levels of greater than 20 mg/dL,
while specimens with creatinine levels between 10 and 20 mg/
dL may be due to increased liquid consumption, dietary habits,
or liquid ingestion preferences. Urine specimens with creatinine
levels between 2 and 10 mg/dL are usually a result of ingestion
of large volumes of water (or other liquid), termed short term
water loading. This is a very common practice when attempting
to dilute a urine so that any drugs in the urine will be diluted
below analytical testing cutoff levels. Urine creatinine levels
below 2.0 mg/dL are usually a result of “dipping”, the direct
addition of a liquid to the urine specimen. Creatinine levels of
0.0 mg/dL indicate the specimen is not consistent with
human urine.
Urine specimens become dilute as a result of the short term
consumption of large amounts of a liquid due to an unknown
stimulus such as a response to heat or exercise, herbal ushes,
prescription diuretics, intentional dilution, or pathological
situations such as diabetes insipidus. The dilution effect from
consuming increased volumes of liquid can last from 2 – 5
hours. Therefore, the increased consumption of liquid would
have to take place between 2 – 5 hours prior to the collection
of the urine specimens.
An important factor to consider when interpreting dilute urine
samples is that drug use can never be assumed unless speci-
cally detected, and conrmed in a urine sample. Certainly, a
dilute sample can produce false negative results, as drugs in
the urine at concentrations near the testing cutoff may be
diluted below the testing cutoff level, however, due to the
reasons stated above it can be difcult to establish the reason
or intent for the sample(s) being dilute. For these reasons, urine
creatinine is reported in conjunction with testing for drugs of
abuse, as an indicator of specimen validity only, as urine
specimens with a creatinine level below 20 mg/dL may have
an increased likelihood of producing a false negative drug
testing result.
For more information about creatinine, refer to page 46.
4. Specic Gravity: Normally, a random urine specimen will
have a specic gravity of greater than 1.003
1
. An extremely
low specic gravity (<1.003) indicates a dilute specimen,
while abnormally high specic gravity (>1.045) may indicate
the presence of dissolved solids such as sodium chloride and
sodium bicarbonate.
5. pH: Normal random urine pH is 4.8-7.8*. Low pH’s indicate pos-
sible ingestion of acidic substances such as cranberry juice or
vinegar; starvation; diarrhea; or direct adulteration of the speci-
men itself with acidic compounds. Elevated pH’s may indicate
the presence of basic compounds such as sodium bicarbonate,
bleach, or Drano; vegetarian diet; or prolonged vomiting. pH
levels of <3 or ≥11 are consistent with adulteration.
6. Visible Blood: Indicates the presence of blood in the urine
specimen. The presence of blood in the urine sample may
adversely impact the testing process and, in addition,
constitutes a biohazard for laboratory employees. Collection
of clean catch urine specimens during menstruation should
be attempted.
Urine adulteration is a double edged sword as both false negative
and false positive results can occur. However, most adulteration
attempts can be detected by either trained collection site person-
nel or by collection procedures as outlined above. Coordination and
cooperation between the collection site and the testing laboratory
provides effective and reliable drugs of abuse testing.
1. Normal ranges are indicated for freshly voided urines only.
Specimen tampering/adulteration continued