This test is designed to determine the presence or absence of gastric acidity. Its greatest advantage is that it eliminates the necessity for passing a tube into the stomach as with the older method. It utilizes a resin-dye combination which is taken orally.

Fast after midnight prior to test. On arising, void and discard the urino.

Take two tablets of caffeine sodium benzoate (250 mg. each) in ana glass of water.

One hour later void and collect the specimen In a bottle labeled "control urine."

Mix axure A-resin compound (2 Gm.) in 1/4 glass of water and drink. Add a little more water for the remaining granules. Do not chow the granules.

Two hours later void and collect tho specimen in a bottle labeled "test urino."

Observe colon If the specimen is dark blue or dark green and it over 60 ml. In volume, the test can be considered sight positive without further laboratory procedures.

Fig. 32. Procedure followed for tubeless gastric analysis.

If free hydrochloric acid is present in the patient's stomach, the dye is broken off and is excreted in the urine, to which it usually imparts a blue color.

In the absence of gastric acid, the resin-dye combination remains intact and there is no urinary color change within the time limit of the test.

Equipment

1. Commercially available kit of Diagnex Blue* which includes the following items.

*E. R. Squibb & Sons, Division of Olin Mathieson Chemical Corporation, New York, N. Y.

(a) Packets of 2 Gm. containing approximately 100 mg. of azure A-resin compound

(b) Two tablets containing 250 mg. of caffeine sodium benzoate* per tablet

(c) Labels for urine bottles

(d) Color comparator block with built-in blue color standard 2. 18% (6N) hydrochloric acid

Method (Fig. 32)

(Instructions for both home and office use are on packet.)

1. The patient fasts after midnight prior to the test.

2. In the morning, he voids and discards all urine.

3. He then swallows the two tablets of caffeine sodium benzoate with one glass of water or receives a subcutaneous injection of 1 ml. of Histalog and drinks a glass of water.

4. One hour later, he voids, collecting all of the sample in an appropriate container labeled "control urine."

5. Following this, he mixes the 2 Gm. of azure A-resin compound in X glass of water and drinks it. Granules remaining in the glass should be rinsed out with a little more water and swallowed. Granules do not dissolve and are not to be chewed.

6. Two hours following ingestion of the azure A-resin compound, the patient voids, collecting all of the urine in an appropriate container labeled "test urine."

7. if the specimen is dark blue or dark green and is over 60 ml. in volume, the test can be considered sight positive without further laboratory procedures. If the test does not meet these criteria, further steps are necessary.**

8. The patient should be informed that he may continue to void colored urine for several days and that this is of no clinical significance.

*Histalog (Eli Lilly and Company, Indianapolis, Ind.), 1 ml. sterile ampules for subcutaneous injection, is available and can be substituted for this oral preparation.

**( 1) The control urine and the test urine are both diluted to a volume of 300 ml. (2) Two test tubes of 10 ml. each of control urine and one test tube of 10 ml. of test urine arc put into the marked slots in the color comparator. (3) Comparison of color is made against a natural light source. The test is positive for free hydrochloric acid if the test sample shows more than 0.6 mg. of azure A per 300 ml. Values between 0.3 mg. and 0.6 mg. are borderline but are considered to represent hypochlorhydric or intermittent acid secretion. (4) If a blue color is not present in the test specimen, 1 drop of 18% hydrochloric acid should be added to all three test tubes. The three tubes are then boiled in a water bath fot ten to fifteen minutes and then allowed to cool to room temperature for two hours. (5) The cooled tubes are replaced in the color comparator and are read as before. If less than 0.3 mg. of azure A-resin is present in the test sample, the test is negative for free hydrochloric acid.

Interpretation Of Results

1. Positive. If the test is positive the patient is assumed to have at least normal levels of free hydrochloric acid in his stomach.

2. False positive. False positive tests have not been described, although a test may be declared positive as a result of a change in color of the urine occurring after the prescribed two-hour interval. This is an error, since such a situation reflects absorption of the dye in the small intestine, and the test should actually be regarded as negative.

3. Negative. A genuinely negative test is presumptive evidence of markedly diminished or absent gastric acidity. The accuracy of the tubeless method compares very favorable with intubation techniques. Before declaring a test negative, one must consider whether any of the factors known to produce a false negative were present.

4. False negative. The following conditions may account for an apparently negative test in the presence of normal gastric acidity:

(a) Intermittent secretion. Some people secrete HCL only intermittently. With them a test can be negative one day and positive the next.

(b) Pyloric obstruction.

(c) Severe liver or kidney disease.

(d) Intestinal malabsorption.

(e) Urinary retention.

(f) Inadequate stimulation of secretory function of the stomach by caffeine. The substitution of histamine or Histalog will overcome this rare defect.

(g) Improper performance of the test.

Management of the patient with negative tubeless gastric analysis Refer to section in chapter on The Stomach (p. 182).