Positive guaiac and bloody stool are poor predictors of intussusception.

BACKGROUND: Currant jelly stool is a late manifestation of intussusception and is rarely seen in clinical practice. Other forms of GI bleeding have not been thoroughly studied and little is known about their respective diagnostic values. OBJECTIVE: To assess the predictive value of GI bleeding (positive guaiac test, bloody stool and rectal bleeding in evaluation of intussusception. METHODS: We performed a retrospective cross-sectional study cohort of all children, ages 1month-6years of age, who had an abdominal ultrasound obtained evaluating for intussusception over 5year period. We identified intussusception if diagnosed by ultrasound, air-contrast enema or surgery. Univariate and a multivariate logistic regression analysis were performed. RESULTS: During the study period 1258 cases met the study criteria; median age was 1.7years (IQR 0.8, 2.9) and 37% were females. Overall 176 children had intussusception; 153 (87%) were ileo-colic and 23 were ileo-ileal. Univariate risk ratio and adjusted Odds ratio were 1.3 (95% CI, 0.8, 2.0) and 1.3 (0.7, 2.4) for positive guaiac test, 1.1 (0.6, 2.1) and 0.9 (0.3, 3.0) for bloody stool, and 1.7 (1.02, 2.8) and 1.3 (0.5, 3.1) for rectal bleeding . CONCLUSION: Blood in stool, whether visible or tested by guaiac test has poor diagnostic performance in the evaluation of intussusception and is not independently predictive of intussusception. If the sole purpose of a rectal exam in these patients is for guaiac testing it should be reconsidered.

Systematic review with meta-analysis: faecal occult blood tests show lower colorectal cancer detection rates in the proximal colon in colonoscopy-verified diagnostic studies.

BACKGROUND: The performance of faecal occult blood tests (FOBTs) to screen proximally located colorectal cancer (CRC) has produced inconsistent results. AIM: To assess in a meta-analysis, the diagnostic accuracy of FOBTs for relative detection of CRC according to anatomical location of CRC. METHODS: Diagnostic studies including both symptomatic and asymptomatic cohorts assessing performance of FOBTs for CRC were searched from MEDINE and EMBASE. Primary outcome was accuracy of FOBTs according to the anatomical location of CRC. Bivariate random-effects model was used. Subgroup analyses were performed to evaluate test performance of guaiac-based FOBT (gFOBT) and immunochemical-based FOBT (iFOBT). RESULTS: Thirteen studies, with 17 cohorts, reporting performance of FOBT were included; a total of 26 342 patients (mean age 58.9 years; 58.1% male) underwent both colonoscopy and FOBT. Pooled sensitivity, specificity, positive likelihood ratio and negative likelihood ratio of FOBTs for CRC detection in the proximal colon were 71.2% (95% CI 61.3-79.4%), 93.6% (95% CI 90.7-95.7%), 11.1 (95% CI 7.8-15.8) and 0.3 (95% CI 0.2-0.4) respectively. Corresponding findings for CRC detection in distal colon were 80.1% (95% CI 70.9-87.0%), 93.6% (95% CI 90.7-95.7%), 12.6 (95% CI 8.8-18.1) and 0.2 (95% CI 0.1-0.3). The area-under-curve for FOBT detection for proximal and distal CRC were 90% vs. 94% (P = 0.0143). Both gFOBT and iFOBT showed significantly lower sensitivity but comparable specificity for the detection of proximally located CRC compared with distal CRC. CONCLUSION: Faecal occult blood tests, both guaiac- and immunochemical-based, show better diagnostic performance for the relative detection of colorectal cancer in the distal colon than in the proximal bowel.

Interval cancers using a quantitative faecal immunochemical test (FIT) for haemoglobin when colonoscopy capacity is limited.

OBJECTIVES: Quantitative faecal immunochemical tests (FIT) for faecal haemoglobin (f-Hb) in colorectal cancer (CRC) screening pose challenges when colonoscopy is limited. For low positivity rates, high f-Hb concentration cut-offs are required, but little is known about interval cancer (IC) proportions using FIT. We assessed IC proportions using an 80 µg Hb/g cut-off. METHODS: In two NHS Boards in the Scottish Bowel Screening Programme, f-Hb was estimated for 30,893 participants aged 50-75, of whom 753 participants with f-Hb ≥ 80 µg Hb/g were referred for colonoscopy. ICs, defined as CRC within two years of a negative result, were identified from the Scottish Cancer Registry. RESULTS: There were 31 ICs and 30 screen-detected (SD) CRCs, an IC proportion of 50.8% (48.4% for men, 53.3% for women). CRC site distribution was similar between ICs and SD, but ICs were later stage (46.7% and 33.3%, Dukes' stages C and D, respectively). Of 31 ICs, 23 had f-Hb < 10 µg Hb/g, including six with undetectable f-Hb. A f-Hb cut-off of 10 µg Hb/g would have raised the positivity rate from 2.4% to 9.4%, increased colonoscopy requirement from 753 to 2147, and reduced the IC proportion to 38.3%. CONCLUSIONS: The IC proportion was similar to that seen with guaiac-based FOBT. The later stage distribution of ICs highlights the benefits of lower f-Hb cut-offs, but with 19.4% of ICs having undetectable f-Hb, some cancers would have been missed, even with drastic reduction in the f-Hb cut-off.

Superior diagnostic performance of faecal immunochemical tests for haemoglobin in a head-to-head comparison with guaiac based faecal occult blood test among 2235 participants of screening colonoscopy.

There is increasing evidence that faecal immunochemical tests (FITs) for haemoglobin offer a number of advantages over traditional guaiac based faecal occult blood tests (gFOBTs). However, evidence on diagnostic performance from direct comparisons with colonoscopy findings in all participants in the average risk population is still sparse. We aimed for a head-to-head comparison of three quantitative FITs with a gFOBT among participants of the German screening colonoscopy programme. Pre-colonoscopy stool samples and colonoscopy reports were obtained from 2235 participants of screening colonoscopy in 2005-2009. To enhance comparability of diagnostic performance of the various tests, we assessed sensitivity, specificity, predictive values and likelihood ratios of FITs after adjusting the FIT cut-off haemoglobin (Hb) concentrations in such a way that FIT positivity rates equalled the positivity rate of the gFOBT. Colorectal cancer, advanced adenomas and other adenomas were found in 15 (0.7%), 207 (9.3%) and 398 (17.8%) participants. The gFOBT was positive in 111 (5.0%) participants, with sensitivities (specificities) for detecting colorectal cancer, any advanced neoplasm or any neoplasm of 33.3% (95.2%), 8.6% (95.4%) and 5.5% (95.2%). At the same positivity rate, all three FITs outperformed the gFOBT in all indicators. In particular, all sensitivities of FITs were approximately two to three times higher at increased levels of specificity. All differences were statistically significant, except for some of the performance indicators for colorectal cancer. In conclusion, FITs can detect much larger proportions of colorectal neoplasms even if their cut-offs are set to levels that ensure equally low positivity rates as gFOBT.

Comparison of guaiac and immunological fecal occult blood tests in colorectal cancer screening: the patient perspective.

OBJECTIVE: Colorectal cancer (CRC) screening programs can decide upon the type of fecal occult blood test (FOBT): the guaiac FOBT (g-FOBT) or the immunological FOBT (i-FOBT). The effectiveness of any screening program depends not only on the diagnostic performance of the screening test but also on the compliance and general acceptance of the test by the public. Any decision on the type of FOBT for CRC screening should also take acceptation and perception into account. The aim of the present study was to study differences in patient perception between i-FOBT and g-FOBT and differences in perception and participation rates among relevant subgroups in a population based study. MATERIAL AND METHODS: Differences in patient perception of i-FOBT and g-FOBT and differences in perception and participation rates among relevant subgroups were investigated (n = 20,623) by sending a short questionnaire to all invited to the first Dutch CRC screening trial. RESULTS: i-FOBT was perceived significantly more favorable than g-FOBT. About 1275 (32%) participants reported the g-FOBT not easy to use, not easy to perform, disgusting or shameful compared to 742 (16%) for the i-FOBT (p < 0.001). The participation rate was significantly higher in those who received i-FOBT compared to the g-FOBT group: 6159 of 10,322 (60%) versus 4839 of 10,301 (47%) (p < 0.001). CONCLUSIONS: These findings support the selection of i-FOBT as the more appropriate test for population screening programs.

Incidence of stool guaiac conversion following extracorporeal shock wave lithotripsy.

OBJECTIVES: To study, in a prospective fashion, acute traumatic effects on the gastrointestinal tract of patients treated by extracorporeal shock wave lithotripsy (ESWL). METHODS: Stool samples from each of 54 patients were tested before and after ESWL for conversion to hemoccult positive. A minimum of one negative pre-ESWL stool guaiac test was required for inclusion into the study. A minimum of two stool guaiac tests were done after ESWL to verify negativity. Patients who converted to a positive hemoccult test after ESWL were then evaluated by colonoscopy for the source of bleeding. RESULTS: Fifty patients completed the study. A single patient (2.0%) converted to a positive post-ESWL hemoccult test and was evaluated with colonoscopy. This patient was found to have two benign adenomatous polyps in the sigmoid and descending colon after treatment for a left renal pelvis calculus. An additional patient with a slightly positive post-ESWL conversion refused further evaluation. The overall post-ESWL conversion rate to guaiac positive, therefore, was less than 4% (2 of 51 patients). CONCLUSIONS: There is no evidence of significant trauma or detectable bleeding in the normal gastrointestinal tract caused by ESWL as measured by postprocedure stool guaiac testing. Guaiac testing of the stool after ESWL may unmask pre-existing gastrointestinal disease. Therefore a positive guaiac test after ESWL warrants further evaluation. This study reaffirms that ESWL is a safe, minimally invasive technique for the treatment of urolithiasis, without significant adverse side effects on the gastrointestinal tract.

Effect of iron on the guaiac reaction.

Most studies show that oral ingestion of iron does not cause a positive stool guaiac reaction. However, all in vitro studies show that iron does cause a positive guaiac reaction and some in vivo studies have shown a positive stool guaiac reaction in response to oral iron. This study examines this unresolved question. Twenty-five normal volunteers were given 900 mg of ferrous sulfate a day. Two Hemoccult II and two HemoQuant tests were obtained before and during iron therapy. All Hemoccult II tests were negative before and after oral iron. Four HemoQuant tests were slightly elevated before oral iron and one was slightly elevated after oral iron. Ferrous sulfate, 300 mg, was dissolved in 1 L of water. The solution was acidic (pH = 3.9) and produced a positive Hemoccult II test. When the solution was titrated with sodium hydroxide to a pH of greater than or equal to 6.0, iron precipitated out and the mixture no longer produced a positive Hemoccult II reaction. Our data show that ferric iron (Fe3+) in solution will give a positive guaiac reaction directly and ferrous iron (Fe2+) will give a positive guaiac reaction after hydrogen peroxide is added because it oxidizes Fe2+ to Fe3+. Iron solutions are acidic and when titrated toward a neutral pH, the iron is precipitated out and the solution is then guaiac-negative. Thus, our in vivo data confirm most previous in vivo studies; furthermore, the discrepancy between in vivo and in vitro studies can be explained as a pH-dependent phenomenon of in vitro iron solutions. Oral iron should not cause a positive guaiac reaction, and the HemoQuant results show no increase in occult blood loss in subjects on oral iron therapy.

Cow milk feeding in infancy: gastrointestinal blood loss and iron nutritional status.

Eighty-one normal infants were studied between 112 and 196 days of age. Thirty-nine infants were fed pasteurized cow milk and the remainder were fed either Enfamil or heat-treated cow milk. During the age interval of 112 to 140 days, the proportion of infants with guaiac-positive stools was significantly (P less than 0.01) greater among infants fed pasteurized cow milk than among those fed Enfamil or heat-treated cow milk. Similarly, infants fed cow milk had a significantly (P less than 0.001) greater number of guaiac-positive stools than did the other infants. After 140 days of age, there was no difference between feeding groups in the number of guaiac-positive stools. No significant differences were observed in mean hemoglobin, hematocrit, serum iron, total iron-binding capacity, or transferrin saturation between feeding groups nor between infants with and those without guaiac-positive stools, It is concluded that pasteurized cow milk should not be fed before 140 days of age.

Screening for colorectal cancer.

A voluntary colorectal screening program was carried out in North Carolina to evaluate the public's willingness to perform a do-it-yourself bowel test, to educate the public on the importance of routine colorectal screening, and to assess the efficacy of a small-scale screening program in detecting colorectal cancer. A screening kit was requested by 1,204 individuals after hearing or reading about the program; 770 kits were returned. Of 29 (3.7%) positive test results, six were negative after retesting. Adequate follow-up was available for 18 of the remaining 23 positive results. Thirteen were due to anal bleeding, diverticulosis, or heavy ingestion of aspirin; five were considered false-positive results, since no evidence of disease could be found. No cases of polypoid tumors or carcinoma were detected. The main value of such a program in an area with a small population base is to increase the awareness of the public of the importance of routine screening for colorectal cancer.