in the dessicant pouch. The results of the test must be
correlated with clinical findings
Problem: Delayed Positive Results
1. Urine/serum sample used for testing is used immediately
after removal from the refrigerator
Bring the urine/serum samples to be tested to room temperature before
Problem: False Negative Results
the highest concentration of hCG, however, if testing is not immediate, the
urine specimen may be stored at 2–8°C for up to 72 hours
Similarly, if fresh serum if used as sample is preferable, however, serum
samples may be stored at 2–8°C for up to 24 hours, in case of delay in
2. Inadequate quantity of sample dispensed in the sample
Dispense exactly 2 drops of urine/serum sample in the sample well.
3. In case of dipstick, improper submerging into the urine/
Dip the orange area of the dipstick in the urine/serum specimen submerging
samples at the end of 15 minutes.
5. The kit containing the test device is exposed to very high
temperatures leading to the deterioration of antibodies
The kit should be stored at 4–30°C when not in use
centrifuged, allowed to settle and only the clear supernatant should be used
7. Highly diluted samples or samples of very early
Highly diluted samples or samples of very early pregnancy may not contain
representative levels of hCG. In such cases, if pregnancy is suspected, the
test should be repeated with first morning urine after 48–72 hours after the
1. The pouch may be having pinholes or is in a defected
condition due to which the nitrocellulose membrane has
a tendency of loosing its flow properties
Check the condition of the pouch and observe for pinholes in the pouch if
any before performing the test
2. Change in color of the desiccant accompanying the
A change in color of the desiccant from deep blue to white/pink indicates
absorbance of moisture. In such cases, discard the test device and rerun
Volume secreted/24 h 1000–1500 mL
pH in mouth is usually 7.5–8.0
Specific gravity 1.002 to 1.008
Pepsin and hydrochloric acid (for protein digestion).
Renin for curdling milk, and gastric lipase—a weak
Normal Gastric Constituents in Infants and Children
The stomach of neonates secretes small amounts of
pepsin, renin, and free acid. Almost 4% of otherwise
normal children have achlorhydria, this percentage
gradually rises with age (30% have achlorhydria at age 60
years and above). During the first year of life, the volume
of the residuum is 2–5 mL (pH = 2.6–3.0). Both these rise to
adult levels at 15–20 years of age.
These may include the following:
1. Blood: An important abnormal finding.
2. Food remnants many hours after eating.
3. Large amounts of mucus or bile.
4. Sarcinae, pyogenic bacteria, lactobacilli, yeast cells.
5. Tissue fragments, large amounts of epithelium.
7. Organic acids, e.g. lactic acid, seen in absence of
8. Tubercle bacilli, in pulmonary tuberculosis, by
swallowing of sputum containing Mycobacterium
Routine Gastric Juice Examination
1. Amount: Normal fasting content is 50–100 mL.
a. Blood is red or the color of coffee ground if acid
b. Fresh bile is yellow; old bile is green.
c. In stasis, food colors may persist.
a. Normal is sour or slightly rancid.
b. Fecal in intestinal obstruction.
4. Character: Let stand, note the three layers:
5. Reaction: Acidic—normal pH.
a. Mean values for basal rate of secretion of acid
426 Concise Book of Medical Laboratory Technology: Methods and Interpretations
b. Mean values for 12 hours nocturnal secretion in
Free acid—29 mEq/L or 16.85 mEq/12 hours.
May be due to one of the causes of hematemesis, or may
be due to trauma of passing a tube. Do guaiac or benzidine
2. Qualitative Test for Free HCI (Topfer’s Test)
To 5 drops of gastric juice in evaporating dish, add 1 or 2
Transfer 5 mL of gastric juice to an evaporating dish add
20 mL water. Add 3 drops of Topfer’s reagent and 3 drops of
phenolphthalein, and titrate with N/10 NaOH until the last
trace of red color disappears. This is the amount of NaOH
needed to neutralize the free HCI—this value multiplied
by 20 equals the mEq/L of free HCl. Carry on titrating until
red color of phenolphthalein reappears. The total number
of mL of NaOH used (in both titrations) multiplied by 20
equals the mEq/L of total acidity.
In the fasting state, gastric contents ordinarily contain
0–15% HCl. For gastric juice, the maximum concentration
of HCl is about 0.160 or 160 mEq of HCl/L. The free rather
than total acid primarily determines the pH, which
usually varies in fasting contents from 2.0-1.0, and this
pH range corresponds to an HCl normality (normality =
mEq/L/1000) of about 0.05–0.10. If the normality drops to
0.01 or so, the pH may be about 3.0, and it takes very little
amount of food or any other diluent to bring the pH to 7.0.
Seen usually in achlorhydria only. Add 2 drops of 10%
ferric chloride to one test tube full of water, mix and divide
into 2 test tubes. Add 1 mL of gastric juice to one tube and
compare. Lactic acid gives canary yellow color. Much lactic
acid (over 0.1%) suggests gastric carcinoma.
Place one drop of sediment on a slide and coverslip it.
Look for undigested food particles, blood, mucus, bacteria,
tissue fragments, parasites, sarcinae, yeasts. Lactobacilli
are large nonmotile rods, which stain brown with Gram’s
Normal gastric constituents in adults
Constituents Normal residuum Appetite juice (postseeing/smelling/
Inorganic solids (%) 0.45 0.14
Specific gravity 1.006–1.009 1.007
Total acidity (mEq/L) 10–50 20–100
Total nitrogen (avg: 66 mg%) 51–75
Examination of Gastrointestinal Contents 427
stain and form lactic acid, they occur in stasis in the
Exfoliative cytologic preparations of fresh gastric
washings should be used in the search for gastric
If the test is to be performed in the morning, give nothing
orally after supper the previous night.
This test employs azure-A resin as the indicator (Diagnex
Azure-A carbacrylic resin dissociates in the presence
of acid to yield free azure-A, which is then excreted in
the urine. In the absence of free acid in the stomach, no
azure-A will be released and hence none will appear in the
The test meal consists of caffeine with sodium benzoate
to stimulate gastric secretion and azure-A resin granules as
the indicator substance. Urine is analyzed for azure-A by a
simple colorimetric method. On getting up in the morning,
urine is micturated and discarded. Nil orally till the
completion of the test. The gastric stimulant, either 500 mg
caffeine sodium benzoate or 50 mg Histalog is taken
with a glass of water or else histamine or Histalog can be
administered subcutaneously. One hour later, patient
urinates and discards the sample. Immediately thereafter, 2 g
of azuresin are ingested with half glass of water. Two hours
later, the patient urinates and saves the entire sample. The
sample is diluted to 300 mL with water and a 10 mL aliquot
is placed in each of 3 test tubes. Two of the tubes serve as
color controls and to each of these approximately 300 mg
of L-ascorbic acid is added. This reduces the azure-A to a
colorless form. The tubes are then placed in a comparator
block containing azure-A standards of 0.3 mg/300 mL and
0.6 mg/300 mL. If the color of the test urine is more intense
than that of 0.6 mg standard, the test is completed and the
patient is presumed to secrete hydrochloric acid. If the
color of the test urine is less than that of 0.6 mg standard, a
drop of solution containing 195 mg CuSO4.5H2O in 100 mL
of 18% HCl (Diagnex blue reagent) is added to each of the
3 urine tubes. All three tubes are placed in a boiling water
bath for 10 minutes. After cooling at room temperature for
2 hours, the color development is again compared to the
standard solutions. The results are reported as less than 0.3
to 0.6 mg, or greater than 0.6 mg.
This is strictly a qualitative test. An excretion of greater than
0.6 mg azure-A in 2 hours is considered to be indicative of
HCl secretion, while values less than 0.3 mg are considered
presumptive evidence of anacidity. Values between 0.3 and
0.6 mg represent borderline secretion.
This represents the response of the stomach to endogenous
stimuli, which are continually present in the interdigestive
The minimum requirements include the following:
1. The patient must be in the fasting state and free from
2. All medications influencing gastric secretion must be
3. The patient must be removed from environmental
No comments:
Post a Comment
اكتب تعليق حول الموضوع