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Biomedical subjects

R M Craig

Publications and source records attributed to R M Craig.

At least 19 recordsLinked to original sources
PubMed2001

Improving the serum D-xylose test for the identification of patients with small intestinal malabsorption.

BACKGROUND: D-Xylose absorption testing is a simple, low-cost method of screening for small intestinal malabsorption. The optimum method to measure D-xylose absorption (serum vs. urine testing) is uncertain. GOALS: We present a method of improving the accuracy of D-xylose testing. STUDY: Fifty-one consecutive patients (40 with chronic diarrhea and 5 asymptomatic patients with renal insufficiency) and 6 volunteers with normal renal function were recruited. All received D-xylose, 10 g intravenously and 25 mg orally, on two separate occasions. Serum concentration was determined at baseline and at frequent times thereafter. Area under the curve was calculated to infinity, and D-xylose bioavailability (F) was calculated. A nonlinear model used to derive the relationship between 3-hour D-xylose concentrations and F showed that a value of less than 22.5 mg/dL correlated with an F of less than 60% (malabsorption of D-xylose). A 1-hour D-xylose of less than 20 mg/dL was considered abnormal. RESULTS: Using these indexes for normal 1-and 3-hour D-xylose levels, 90% of patients with D-xylose malabsorption were identified (sensitivity, 90%; specificity, 95%), which represents a marked improvement within the conventional 1-hour D-xylose of less than 20 mg/dL alone (sensitivity, 71%; specificity, 100%). The model was applied prospectively to 15 additional patients with chronic diarrhea. Of these, 12 patients with an F of less than 60% were identified, including 2 patients with normal 1-hour D-xylose levels. CONCLUSIONS: Thus, the addition of a 3-hour D-xylose serum level of less than 22.5 mg/dL to conventional 1-hour D-xylose determination greatly improves the D-xylose test for malabsorption screening.

Adult↗
PubMed2000

D-xylose kinetics and hydrogen breath tests in functionally anephric patients using the 15-gram dose.

Malabsorptive evaluation in renal failure is difficult because most absorptive testing requires urinary collections. Kinetic analysis of d-xylose absorption and d-xylose breath testing were performed in an effort to establish an effective absorption test in functionally anephric patients. We studied 13 fasting renal failure patients with no diarrhea or symptoms suggesting malabsorption on two separate nondialysis days after they received 15 g oral d-xylose on day 1 and 10 g IV on day 2. Serum collections were used to calculate the kinetic rate constants and extent of d-xylose absorption. After the oral d-xylose, end expiratory breaths were collected every 15 minutes for 3 hours and were analyzed for H2 with gas chromatography. Five subjects also allowed upper endoscopy and duodenal biopsy. The mean absorption rate constant (Ka) and bioavailability (F) were similar to published values for normal subjects using the 15-g dose (0.936 min(-1); range, 0.227-1.96; and 74%, range 46-99, respectively). Of the patients, 12 had normal 1-hour serum d-xylose concentrations (>20 mg/dL). There was no clear inverse correlation between the rate constant for absorption or bioavailability and peak breath hydrogen or the area under the curve for breath H2 versus time. Using 15 g oral d-xylose, mean bioavailability and absorption rate constants are normal in functionally anephric patients with no clinical evidence of malabsorption. Three patients had elevated breath peak H2 concentrations, but there was no clear inverse correlation between bioavailability and the breath H2 values. A 1-hour serum dxylose concentration >20 mg/dL may be considered normal in this patient group, similar to patients with normal renal function.

Adult↗
PubMed1999

D-xylose testing.

The literature on D-xylose testing has been reviewed, stressing advances in our understanding of absorption in general (including D-xylose absorption), the relationship of D-xylose testing to the development of excellent serologic tests for the diagnosis of celiac disease, the use of D-xylose testing in the evaluation of diarrhea in acquired immunodeficiency syndrome, new information on breath testing for the evaluation of malabsorption, and recent information on the understanding of D-xylose absorption compared with transcellular vs. paracellular transport. The authors suggest ways in which D-xylose testing might be employed in malabsorption or diarrhea evaluations, including some algorithms.

Adult↗
PubMed1998

Absorptive function following small intestinal transplantation.

All studies involving small intestinal transplantation and absorptive function are reviewed. The effects ischemia-reperfusion, lymphatic disruption, denervation, rejection, immunosuppressive medication, and infection are elucidated as far as the studies allow. Species differences are discussed. Conclusions regarding the major absorptive defects are drawn.

Denervation↗
PubMed1997

Urinary recovery of lactulose compared to D-xylose absorption kinetics in HIV patients with diarrhea and weight loss.

Using a kinetic model of D-xylose absorption, we have previously shown that there is severely impaired absorption of D-xylose in HIV patients with diarrhea and weight loss. The absorptive defect is characterized by an increased rate constant for nonabsorptive loss of D-xylose, Ko, and a decreased absorptive rate constant, Ka, and is unrelated to histology or the presence of pathogens. It is not known if there is also abnormal paracellular transport in these patients. We have extended our observations in these patients by including a measurement of paracellular transport, lactulose absorption. Nine HIV patients with chronic diarrhea, weight loss, and no detectable intestinal pathogens, two healthy volunteers, and three non-HIV patients with chronic diarrhea (two functional and one with scleroderma) were enrolled. Of the nine HIV patients, six had diminished bioavailability of D-xylose, F (range: 19-52%, normal >70%), and elevated rate constant for nonabsorptive loss, Ko (range: 0.54-1.35/hr, normal <0.353/min). Four of the six also had decreased Ka (range: 0.09-0.36/hr, normal >0.634/min). Only one of these six had increased lactulose recovery (3.51%, normal <0.5%). Two of three patients with normal kinetic parameters of D-xylose absorption had increased lactulose urinary recovery (1.92%, 2.61%). In conclusion, lactulose absorption is increased in some patients with HIV-related diarrhea who have normal D-xylose absorption, suggesting a paracellular mechanism for diarrhea in some patients with AIDS enteropathy.

Diarrhea↗
PubMed1997

Randomized, double-blind study of intravenous human albumin in hypoalbuminemic patients receiving total parenteral nutrition.

OBJECTIVE: To determine whether replacement of human albumin will improve a patient's prognosis. DESIGN: A randomized, double-blind, controlled study in which 25 g of human albumin vs. placebo was administered intravenously daily. SETTING: A university-affiliated hospital. PATIENTS: Thirty-six patients with hypoalbuminemia (serum albumin of <2.5 g/dL), receiving total parenteral nutrition. None of the patients had known cancer, cirrhosis, or nephrotic syndrome. INTERVENTIONS: Each patient received at least 6 days of therapy (6 to 24 days of albumin; 7 to 32 days of placebo). Four subjects were excluded from the study since they received therapy for <6 days. One patient was excluded from the study after nephrotic syndrome was identified. Albumin metabolic rates for those patients receiving albumin were estimated using the formula: Metabolism of albumin = 25 g/day + (albumin 1 - albumin 2)(Vd)/days, where albumin 1 and 2 are the serum albumin concentrations (g/L) at the beginning and end of the serum sampling intervals, respectively; Vd is the volume of distribution (L); and days relates to the number of days of the sampling interval. MEASUREMENTS AND MAIN RESULTS: Sixteen patients received albumin; 15 patients received placebo. One patient receiving placebo and two patients receiving albumin died within 30 days. One patient who received placebo and three patients who received albumin developed sepsis or bacteremia; four patients who received placebo and seven patients who received albumin developed pneumonia during the study (NS). The serum albumin increased in all patients receiving intravenous albumin, but one patient received intravenous albumin for only 6 days. The mean serum albumin concentration increased by 1.42 g/dL in the albumin patients, and increased by 0.29 in the placebo patients (p < .0001 by unpaired t-test). Mean initial albumin metabolism was 17.4 g/day (0.3 g/kg/day). At the end of therapy, albumin metabolism was 20.5 g/day (0.36 g/kg/day) (paired t-test, p = .4, NS). CONCLUSIONS: a) The administration of intravenous albumin to hypoalbuminemic patients receiving total parenteral nutrition does not improve morbidity or mortality. b) Albumin metabolic rates, initially related to the catabolic state, are high; later, these rates are high related to filling of the albumin space and gluconeogenesis. c) On the basis of the high albumin catabolic rates at the end of the infusion, doses of albumin of <25 g/day might be sufficient to replace albumin stores.

Double-Blind Method↗
PubMed1995

Intense nutritional support in inflammatory bowel disease.

The value of intense nutritional support in inflammatory bowel disease is still debated. Claims have been made that total enteral nutrition is as effective as total parental nutrition. In this review, the use of parenteral and enteral nutritional support as primary therapy in patients with inflammatory bowel disease has been critically evaluated. Most studies have been uncontrolled and nonrandomized with short-term follow-up. The literature does suggest, however, that intense nutritional support may have an adjunctive role to drug therapy in achieving remission in Crohn's disease, especially in corticosteroid-refractory patients. Nutritional support has a lesser role in chronic ulcerative colitis, except for assistance in pre- and postoperative management. The data do not support one variety of nutritional support over another, although enteral support should be used if possible, as it is less costly and potentially less complicated.

Food, Formulated↗
PubMed1995

D-xylose hydrogen breath tests compared to absorption kinetics in human patients with and without malabsorption.

The D-xylose breath H2 test may be useful in characterizing intestinal absorptive function. Our aim was to determine whether breath H2 following D-xylose administration reflects the extent to which the D-xylose is absorbed by comparing it to a kinetic model of D-xylose absorption. Twenty-five subjects were studied. They ingested 15 g D-xylose on the first day and 25 g D-xylose on the third day. On the second day they received 10 g intravenous D-xylose along with 15 g oral lactulose. Multiple serum and urine samples were obtained for D-xylose content to calculate its rate constants and extent of absorption by multicompartmental analysis. Breath H2 determinations were obtained every 15 min for 3 hr following the 15 g D-xylose and lactulose ingestion. Peak breath H2 concentration correlated with extent of absorption (r = -0.787, P < 0.001), K0, the rate constant for nonabsorptive loss (r = 0.744, P < 0.001), and 5-hr urine content (r = -0.705, P < 0.001). Area under the breath H2 curve also correlated with these parameters: extent of absorption (r = -0.770, P < 0.001), K0 (r = 0.662, P < 0.001), 5-hr urine content (r = -0.629, P < 0.012). Peak D-xylose breath H2 to peak lactulose breath H2 showed no correlation with extent of absorption. The extent of absorption was higher with the 15-g dose than the 25-g dose in all patients tested (P < 0.01). (ABSTRACT TRANCATED AT 250 WORDS)

Administration, Oral↗
PubMed1995

Pyogenic granuloma in Barrett's esophagus mimicking esophageal carcinoma.

A 31-year-old white man with a history of testicular carcinoma and lymphoma developed severe reflux esophagitis with stricture formation requiring repeated dilatation. Barrett's esophagus was histologically confirmed. The Barrett's mucosa was observed endoscopically and became polypoid, mimicking an esophageal carcinoma. The polyp was evaluated by endoscopic ultrasonography and ultrasonically guided aspiration cytology. It was managed by snare cautery removal, which showed a pyogenic granuloma.

Adult↗
PubMed1994

Malabsorption and deficiency of vitamin B12 in HIV-infected patients with chronic diarrhea.

Deficiency of vitamin B12 is commonly reported in HIV-infected patients. We measured vitamin B12 levels in 36 HIV-infected patients with chronic diarrhea (> 3 stools/day for six weeks or more). Eight patients had an identifiable cause of diarrhea. Vitamin B12 levels were low in 39%. Sixteen of these patients were selected to undergo further testing, eight patients with low levels of vitamin B12 and eight with normal B12 levels. These 16 patients had both a stage II Schilling test and measurement of multiple serum D-xylose concentrations performed after both oral and intravenous doses of D-xylose. Integrated areas under the curves (AUC) for D-xylose concentration versus time were calculated for intravenous and oral doses, and D-xylose bioavailability was determined. Stage II Schilling tests were abnormal in 11 patients, (69%). D-Xylose bioavailability correlated closely with vitamin B12 absorption (r = 0.648, P < 0.01). Comparisons of mean values for CD4 count, serum albumin, Karnovsky score, six-month weight loss, 1-hr serum D-xylose levels and MCV failed to reveal a significant difference between those with and without abnormal serum vitamin B12 levels. These data indicate that below-normal levels of vitamin B12 are highly prevalent in HIV-infected patients with chronic diarrhea. Malabsorption of vitamin B12 occurs in the setting of an enteropathic process effecting both the proximal and distal small bowel. Since no risk factors for vitamin B12 deficiency could be identified, screening for vitamin B12 deficiency in HIV-infected patients with chronic diarrhea is strongly recommended.

Chronic Disease↗
PubMed1994

Hepatotoxicity related to total parenteral nutrition: comparison of low-lipid and lipid-supplemented solutions.

PURPOSE: Because it is unclear whether or not the lipid or carbohydrate component of total parenteral nutrition solutions determines the development of cholestasis during total parenteral nutrition, a prospective randomized clinical trial of a predominantly carbohydrate solution (group I) versus one with isocaloric substitution of 30% nonprotein calories with lipid (group II) was performed. METHODS: Twelve patients in group I, 4 female and 8 male, and 14 patients in group II, 8 female and 6 male, were studied. Each subject received 100% to 150% of the basal energy needs, determined by the Harris-Benedict equation. Amino acids were supplied to provide a protein:kilocalorie ratio of 1:150 to 200. There were no differences between the groups in terms of mortality, nitrogen balance, and maintenance of weight. Weekly serum aspartate aminotrasferase (AST) and alkaline phosphatase (AP) levels were obtained. The change from baseline values was calculated. RESULTS: The observed difference between the two groups for AST was 5.7 (higher for group II), P = .55, and for AP, 39.1 (higher for group I), P = .23. A power calculation was performed to determine the number of patients required for a statistically significant difference in AP between the two groups with an alpha of 0.05 and a power of 0.85:67 patients. CONCLUSIONS: With these statistical considerations, we conclude that there was probably no statistically significant difference between the groups for an increase in AST or AP levels during total parenteral nutrition.

Adult↗
PubMed1994

The effect of total parenteral nutrition on serum albumin.

Our objective was to assess whether the serum albumin level rises in patients given total parenteral nutrition (TPN). All randomized controlled studies of TPN for at least 7 days versus oral therapy were reviewed. Data on serum albumin had to be available to be acceptable for analysis. Only trials of patients with cancer fulfilled these selection criteria for our analysis. None of the reported studies showed a significant rise in serum albumin with TPN when compared to controls. The mean change in serum albumin levels for all of the studies was -0.3 g/dl in the TPN group and -0.3 g/dl in the control group. In published randomized controlled studies of TPN versus oral diet, there is no significant increase in serum albumin levels in those receiving TPN or decrease in serum albumin in controls. Our study does not support the serum albumin level as a nutritional marker in patients with cancer.

Biomarkers, Tumor↗
PubMed1994

Small intestinal HIV-associated enteropathy: evidence for panintestinal enterocyte dysfunction.

To characterize the absorptive defect of AIDS enteropathy, we have used a D-xylose kinetic model of proximal absorption and correlated these findings with Schilling's test for cobalamin absorption, measurements of distal intestinal function. In addition, we compared findings between duodenal and jejunal biopsy and aspirations to determine whether additional information can be obtained by sampling the more distal site. Twelve consecutive patients with AIDS who had 3 to 14 loose bowel movements per day and two stool study results negative for pathogens, were admitted for study. D-xylose testing with oral and intravenous doses was used to determine the rate constants for D-xylose absorption, Ka, and the rate constant for nonabsorptive loss, Ko. Duodenal and distal duodenal-jejunal endoscopic aspirations and biopsies were also performed. Minimal histologic abnormalities were seen in either the proximal or distal biopsy sites. There were no significant differences in mucosal blunting, abnormalities of the enterocytes, lamina propria infiltrate, or presence of microorganisms between duodenal and distal duodenal-jejunal sites. Seventy-five percent had no identifiable pathogens. Ten of 12 patients had diminished Ka, elevated Ko, or both. Two patients had a normal Ka and Ko. Eight of 10 had an abnormal Schilling's test result. Percentage weight loss correlated negatively with Ka (r = 0.75; p = 0.013) and with Schilling's test results (r = 0.65; p = 0.043. Ka correlated positively with Schilling's test results (r = 0.82; p = 0.004).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗