Evaluation of a String Test in Nonbleeding Individuals

Vol. 58, No.2 Printed in U.S.A.

GASTROENTEROLOGY

Copyright © 1970 by The Williams & Wilkins Co.

EVALUATION OF A STRING TEST IN NONBLEEDING INDIVIDUALS DONALD M. SWITZ, M.D ., AND HAROLD P. ROTH, M.D. Veterans Administration Hospital and the Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio

Using the commercially available gastrointestinal string, type 2, we evaluated the string test without fluorescein in 15 volunteers who had no evidence of gastrointestinal tract disease or bleeding. Six subjects (40 %) had significant blood stains on the string using Smith's criteria. Such a large proportion of false positive results emphasizes the limited diagnostic usefulness of this variation of the string test.

It often is difficult to localize the source of upper gastrointestinal blood loss. X-ray examination frequently does not identify the site. Endoscopy, also often not diagnostic, entails patient discomfort as well as risk. A string test for the localization of upper gastrointestinal bleeding was proposed by Einhorn in 1909 1 as an easily performed diagnostic measure with little discomfort or risk to the patient. A silk thread 75 cm in length was swallowed in the evening, removed the next morning, and examined for blood stains. Pittman has designed a commercially available modern counterpart, which includes radio-opaque markers (GI String, type II, Advanced Laboratory Associates, 517 Milltown Road, North Brunswick, N. J.) , and has used it in a large group of patients. 2 Although the string test has been reported to be accurate in the localization of upper gastrointestinal bleeding, the possibility of false positive results has not been recognized widely. We therefore undertook an evaluation of the incidence of false positive results, using the string and the procedure described by Received September 27, 1968. Accepted August 22, 1969. Address requests for reprints to: Dr. Donald M . Switz, 1846 35th Street, N.W., Rochester, Minnesota 5590l. The authors wish to thank Natalie Maxymiv for grading the string tests.

Pittman,2 in patients without gastrointestinal bleeding. We have shown that this string often is stained significantly with blood in nonbleeding, apparently normal control subjects. Materials and Methods Subjects were selected from patients admitted to the minor surgery, dermatology, urology, cardiology, and pulmonary services of the Cleveland Veterans Administration Hospital. They were excluded if they were not ambulatory or had gastrointestinal symptoms, a past history of gastrointestinal disease, a disorder with gastrointestinal tract manifestations, a history of ingestion of gastric irritants (aspirin or alcohol) during the preceding week, an· abnormality on physical examination of the abdomen, anemia (hematocrit <40%), positive Rumpel-Leedes test, or guaiac-positive stool samples (one to three tests). The charts of 304 patients were examined; 72 fulfilled these criteria. Each patient was interviewed and examined; 22 agreed to participate. All patients were male and ranged from 21 to 68 years of age. The string described by Pittman2 was purchased. It was made of braided tape 5 feet long and Y-i inch wide with radio-opaque horizontal and longitudinal markings. As recommended by Haynes and Pittman: and in the brochure supplied with the string, 2 ml of ·mercury (27 g) were secured at the leading end inside a double layer of finger cots (the tractor) . The string was introduced exactly after the method of Pittman2 ; no fluorescein was used. The test was performed after an 8-hr fast. The progress of the string was followed by fluoros185

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copy. The patient was placed on an X-ray table, tilted to 60 degrees from the horizontal, and urged to swallow the moistened string. If unsuccessful he gargled with 5 ml of 10/0 xylocaine for 5 min. Once the weight was swallowed, the patient was turned to his left side and urged to swallow the string to the 2Y2foot mark within 10 min. When the weight was in the stomach the patient sat up, leaned forward, and took seven deep breaths. He then lay flat on his right side and was encouraged to swallow the remainder of the string during the next 2 hr. When the weight reached the ligament of Treitz, abdominal films were taken in the supine and left lateral decubitus positions and the string was removed gently and slowly. The string was examined by an independent observer for gross discoloration. Stains were graded 1 to 4+ using the colors of the Tallqvist hemoglobin color scale as a guide; the presence of blood was confirmed by guaiac test' of the string. As we did not use fluorescein, Pittman's criteria would have been: gross blood or guaiac-positive reaction (group A or C), no blood or guaiac reaction (group B or D). Since Pittman's criteria allowed no gradation of results, the criteria of Smith" were used: no blood or guaiac-positive response, 0 ; only guaiac positive, 1+; light superficial blood stain, 2+; penetrating stains, 3+; gross blood clot, 4+. TABLE

Patient

Gross Guaiac test Grading blood by (most (strongSmith's est intense reaccriteria stain) tion)

1 2 3 4 5 6 7 8 9 10

11 12 13 14 15

3+ 3+ 2+ 3+ 0 0

4+ 3+ 0 4+ 0

1+

0 0 3+ 3+ 4+ 4+ 2+ 0 4+

0 2+ 2+ 3+ 4+ 3+ 0

1+

1+

Most proximal stain

Results Difficulties encountered. Twenty-two patients entered the study, but 5 were unable to swallow the string because of persistent gagging, 1 had asymptomatic duodenal diverticuli discovered by X-ray, and another refused radiological examination. Thus, 15 patients swallowed the string and had a normal upper gastrointestinal X-ray. If the patient lay on his right side only (after initial passage of the string), as suggested by Pittman, the tractor often remained in the first or second portion of the duodenum; in 9 of 15 patients (60%) the tractor was in this location after 2 hr. We turned the patient to his left side after this period to hasten passage to the ligament of Treitz and to allow evaluation of

Cumulative length of tape Blood Total durashowing on tion greater edge than of tape of test 1+ blood stain

inches

3+ 3+ 0 3+ 0

Midesophagus Cardia Cardia Cardia

1+

Distal esophagus Cardia

0 0 2+ 2+ 3+ 3+ 3+ 0 2+

We have designated as positive those strings that are 3 to 4+ by Smith's criteria, since it was in such cases that he found the best correlation with active lesions. All subjects had an upper gastrointestinal X-ray examination within several days of the string test.

1. Quantitation and location of blood on Siring

-- ----

a

Vol. 58, No.2

SWITZ AND ROTH

Cardia Fundus Cardia Distal esophagus Cardia Midesophagus

Extensively evaluated, no cause found.

1~

3

%

2:Y.1 0 0 0 0

:Y.I ~'2

6 8 4 0

~~

Primary diagnosis

-- -min

0 0 0 + 0 0 + 0 + + + + 0 0 +

180 155 175 150 190 180 155 145 160 125 160 175 135 70 160

Paronychia Functional abdominal pain" Psoriasis Plantar wart N eurodermati tis Basal cell epithelioma Bronchiectasis Inguinal hernia, repaired Eczematous dermatitis Stab wound Stasis ulcers Umbilical hernia Tonsillectomy Pulmonary nodule Sebaceous cyst

THE PITTMAN STRING TEST

February 1970

the entire duodenum. The time from swallowing to string removal averaged 2Y2 hr. The string passed beyond the ligament of Treitz in 12 patients. In 2 patients (7 and 9, table 1) the string never left the stomach. In 1 (13, table 1) it did not leave the first portion of the duodenum. Patients 9 and 13 stated that they were unable to swallow more than 2 feet of string. All 3 patients had gross blood on the string after removal. In one instance a mercury-filled tractor was lost during withdrawal; it passed per rectum without incident. Presence oj blood. After removal, blood was observed on 11 strings; two of these (from patients 3 and 7) were guaiac-negative (both spots were light and small; they were graded Smith 0). One string was negative to inspection but was guaiacpositive (Smith 1+ ) . . Six strings were significantly positive (3 to 4+ by Smith's criteria) ; on 5 of these gross blood or guaiac-positive areas were scattered diffusely. In 3 of the 6, spots were seen on the edge as well as on the flat part of the string. The highest site of bleeding in the 6 significantly positive strings (as determined bf the location of the most proximal staini was the mjdor dIstal esophagus in 2 cases and the gastric cardIa in the remainder. Some o( the blood spots dIstal to these sites might have accumulated as the string passed a bleeding point during passage or retrieval. Because we suspected that minimal bleeding might produce a strongly guaiacpositive reaction on the string, 1 drop of blood with hematocrit of 40% was spotted; , it gave a 4+ guaiac reaction. One blood spot with 6% hematocrit also yielded a 4+ test response and 1 spot with 1% hematocrit yielded a 3+ test. Guaiac test of the string is very sensitive; minimal mucosal abrasion may yield enough blood to give a 3+ guaiac test response. Discussion

The most important observation of our study was that 12 of 15 patients (80%) with apparently normal upper gastrointestinal tracts had gross blood and/or guaiac-positive areas on the Pittman-de-

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signed string and, especially, that 6 of these (40%) were 3 to 4+ by Smith's criteria. Since 1 drop of diluted blood (hematocrit, 1%) spotted on the string will give a 3+ response with guaiac, clinically insignificant blood loss may yield a false-positive string test if guaiac-positive response is the only criteria. Smith5 has pointed out that strings (of his design) which were guaiac-positive alone or showed only slight blood stains might represent falsely positive tests; however, he also found that penetrating stains or clots (3 to 4+ test) correlated well with proven lesions. We found stains or clots that would be graded Smith 3+ or 4+ in 6 of 15 patients (40%) without evidence of gastrointestinal disease when using the commercially available Pittman string. Neither the presence nor the site of bleeding can be determined accurately by a diagnostic test that yields a high proportion of falsely positive results. Review of the literature suggests that false positives have been encountered but not always recognized. In Einhorn's case 13,1 tests for occult blood in stomach contents and feces were negative, although the string test was positive. Twenty-one of Pittman's 82 patients2 with gross blood, guaiac-positive stains, and/or fluorescein stain on strings did not have a clinically demonstrable bleeding site: Others have recognized the problem. Ewart and co-workers 6 found the Einhorn string test unreliable because of poor correlation with proven lesions or absence of lesions in 25 patients with and without gastrointestinal disease. Rappaport7 considered all stains at the pyloroduodenal and esophagogastric levels falsely positive, and Smith 5 emphasized that negative (rather than positive) results might be more reliable unless the observations reached 3 to 4+ by this criteria. Fluorescein dye was omitted in this study because (1) Pittman noted dye alone in only 2 out of 122 cases known to be bleeding, (2) allergic responses have been reported, and (3) local pain occurs if the dye is extravasated. 2 We felt that little would have been added by its use. The cardioesophageal area (table 1) was

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SWITZ AND ROTH

Vol. 58, No.2

the most proximal site of significant false positive stains. This finding and the frequent presence of blood on the rough edge of the string suggest that mucosal trauma may have been a cause of the false positive results. The relatively heavy tractor may pull the rough edge of the string taut against the cardioesophageal junction abrading the mucosa sufficiently to yield blood stains that are scattered diffusely as the string passes the bleeding point. A lighter tractor (as used by Smith and others), another type of string, or different method of passage might decrease or eliminate false positive tests. If the commercially available Pittman string is so modified, however, data on patients who are not bleeding will be required to establish this point.

2. Pittman, F. E. 1964. The fluorescein string test. An analysis of its use and relationship of barium studies of the upper gastrointestinal tract in 122 cases of gastrointestinal tract hemorrhage. Ann. Intern. Med. 60 : 418429. 3. Haynes, W. F., and F. E. Pittman. 1960. Application of the fluorescein string test in 32 cases of upper gastrointestinal hemorrhage. Gastroenterology 38: 690--697. 4. Page, L. B., and P. J. Culver. 1961. Syllabus of laboratory examinations in clinical diagnosis, p. 377. Harvard University Press, Cambridge, Mass. 5. Smith, V. M. 1961. String impregnation test ("string test") for lesions of the upper digestive tract. Ann. Intern. Med. 64: 16-29. 6. Ewart, J. A., H. N . Sturtevant, and B. H. Sullivan, Jr. 1960. An evaluation of the Einhorn string test. Amer. J. Dig. Dis. 6:

REFERENCES

7. Rappaport, E. M. 1955. Modified string test for determination of the site of upper gastrointestinal bleeding. Gastroenterology 28: 1016-1026.

1. Einhorn, M. 1909. A new method of recogniz-

ing ulcers of the upper digestive tract and of localizing them . M ed. Rec. 75: 549-555.

632-638.