Occult blood and fecal leukocytes as screening tests in childhood infectious diarrhea: an old problem revisited

Evaluation of Fecal Inflammatory Biomarkers to Identify Bacterial Diarrhea Episodes: Systematic Review and Protocol for the Enterics for Global Health Shigella Surveillance Study

Background

The measurement of fecal inflammatory biomarkers among individuals presenting to care with diarrhea could improve the identification of bacterial diarrheal episodes that would benefit from antibiotic therapy. We reviewed prior literature in this area and describe our proposed methods to evaluate 4 biomarkers in the Enterics for Global Health (EFGH) Shigella surveillance study.

Methods

We systematically reviewed studies since 1970 from PubMed and Embase that assessed the diagnostic characteristics of inflammatory biomarkers to identify bacterial diarrhea episodes. We extracted sensitivity and specificity and summarized the evidence by biomarker and diarrhea etiology. In EFGH, we propose using commercial enzyme-linked immunosorbent assays to test for myeloperoxidase, calprotectin, lipocalin-2, and hemoglobin in stored whole stool samples collected within 24 hours of enrollment from participants in the Bangladesh, Kenya, Malawi, Pakistan, Peru, and The Gambia sites. We will develop clinical prediction scores that incorporate the inflammatory biomarkers and evaluate their ability to identify Shigella and other bacterial etiologies of diarrhea as determined by quantitative polymerase chain reaction (qPCR).

Results

Forty-nine studies that assessed fecal leukocytes (n = 39), red blood cells (n = 26), lactoferrin (n = 13), calprotectin (n = 8), and myeloperoxidase (n = 1) were included in the systematic review. Sensitivities were high for identifying Shigella, moderate for identifying any bacteria, and comparable across biomarkers. Specificities varied depending on the outcomes assessed. Prior studies were generally small, identified red and white blood cells by microscopy, and used insensitive gold standard diagnostics, such as conventional bacteriological culture for pathogen detection.

Conclusions

Our evaluation of inflammatory biomarkers to distinguish diarrhea etiologies as determined by qPCR will provide an important addition to the prior literature, which was likely biased by the limited sensitivity of the gold standard diagnostics used. We will determine whether point-of-care biomarker tests could be a viable strategy to inform treatment decision making and increase appropriate targeting of antibiotic treatment to bacterial diarrhea episodes.

Testing for Chronic Diarrhea

Chronic diarrhea is a frequently encountered symptom in clinical practice. The etiologies for chronic diarrhea are diverse and broad with varying clinical implications. A useful method of categorizing chronic diarrhea to guide a diagnostic work-up is a pathophysiology-based framework. Chronic diarrhea may be categorized as malabsorptive, secretory, osmotic, and inflammatory or motility related. Frequently, overlap between categories may exist for any given diarrhea etiology and diagnostic testing must occur with an understanding of the differential diagnosis. Investigations to achieve a diagnosis for chronic diarrhea range from screening blood and stool tests to more directed testing such as diagnostic imaging, and endoscopic and histological evaluation. The pathophysiology-based framework proposed in this chapter will allow the clinician to select screening tests followed by targeted tests to minimize cost and complications to the patient, while providing a highly effective method to achieve an accurate diagnosis.

Clinical Symptoms of Human Rotavirus Infection Observed in Children in Sokoto, Nigeria

Rotavirus has been identified among the most important causes of infantile diarrhoea, especially in developing countries. The present study was undertaken to determine the occurrence and clinical symptoms of human rotavirus disease among children presenting with varying degree of diarrhoea in selected urban hospitals in Sokoto metropolis, Nigeria. Diarrhoea samples were collected from 200 diarrheic children younger than 5 years of age and tested using a commercially available DAKO Rotavirus ELISA kit which detects the presence of human group A rotaviruses. A questionnaire, based on WHO generic protocol, was completed for each child to generate the primary data. Of the total number of samples collected, 51 were found to be positive for human group A rotavirus indicating 25.5% prevalence of the disease in Sokoto state. The symptoms associated with the disease were analyzed and discussed.

Evaluation of faecal calprotectin as a valuable non-invasive marker in distinguishing gut pathogens in young children with acute gastroenteritis

AIM

The aim of the study is to evaluate faecal calprotectin (f-CP) in children ≤3 years of age with acute gastroenteritis (AG) as an early predictor of bacterial inflammation.

METHODS

We prospectively analysed f-CP levels and diagnostic workup in 107 consecutive children (66 AG, 41 controls).

RESULTS

Children with bacterial AG (BAG) was found to have higher diarrheal frequency (p < 0.01), fever (p < 0.01), erythrocyte sedimentation rate (p < 0.001), white blood count (p < 0.01) and C-reactive protein (CRP) (p < 0.001) compared with viral AG (VAG). Vomiting was frequent in VAG (p < 0.001). f-CP negatively correlated with age in controls (r = -0.5998). BAG demonstrated significantly higher f-CP levels [median, 219 μg/g, interquartile range (IQR): 119-350.2] compared with VAG (49.3 μg/g, IQR: 8.8-131.1) as well as controls (26.5 μg/g, IQR: 14.9-55.1) (p < 0.001). VAG and control f-CP levels were similar. f-CP was the best-rated marker of BAG with a diagnostic accuracy of 92%. Receiver-operator characteristic analysis revealed an area under curve of 0.95 for identifying BAG; sensitivity and specificity of f-CP were 93% and 88%, respectively, at an adjusted cut-off point of 103.9 μg/g faeces. Combined f-CP and CRP yield improved diagnostic accuracy of 94% for BAG.

CONCLUSION

f-CP facilitates early discrimination between bacterial and viral causes of AG in young children. Combining f-CP with CRP increases the diagnostic power of diagnosing BAG.

Shiga toxin 2 and flagellin from shiga-toxigenic Escherichia coli superinduce interleukin-8 through synergistic effects on host stress-activated protein kinase activation

Shiga toxins expressed in the intestinal lumen during infection with Shiga-toxigenic Escherichia coli must translocate across the epithelium and enter the systemic circulation to cause systemic (pathological) effects, including hemolytic uremic syndrome. The transepithelial migration of polymorphonuclear leukocytes in response to chemokine expression by intestinal epithelial cells is thought to promote uptake of Stx from the intestinal lumen by compromising the epithelial barrier. In the present study, we investigated the hypothesis that flagellin acts in conjunction with Shiga toxin to augment this chemokine expression. We investigated the relative contributions of nuclear factor kappaB (NF-kappaB) and mitogen-activated protein kinase (MAPK) signaling to transcription and translation of interleukin-8. Using reporter gene constructs, we showed that flagellin-mediated interleukin-8 gene transcription is heavily dependent on both NF-kappaB and extracellular signal-regulated kinase 1 and 2 (ERK-1/2) activation. In contrast, inhibition of p38 has no detectable effect on interleukin-8 gene transcription, even though flagellin-mediated activation of host p38 is critical for maximal interleukin-8 protein expression. Inhibition of MAPK-interacting kinase 1 suggests that p38 signaling affects the posttranscriptional regulation of interleukin-8 protein expression induced by flagellin. Cotreatment with Stx2 and flagellin results in a synergistic upregulation of c-Jun N-terminal protein kinases (JNKs), p38 activation, and a superinduction of interleukin-8 mRNA. This synergism was also evident at the protein level, with increased interleukin-8 protein detectable following cotreatment with flagellin and Stx2. We propose that flagellin, in conjunction with Shiga toxin, synergistically upregulates stress-activated protein kinases, resulting in superinduction of interleukin-8 and, ultimately, absorption of Stx into the systemic circulation.

Association of enterotoxigenic Bacteroides fragilis infection with inflammatory diarrhea

BACKGROUND

Diarrheal illnesses remain a leading cause of morbidity and mortality globally, with increasing recognition of long-term sequelae, including postinfectious irritable bowel syndrome and growth faltering, as well as cognitive deficits in children. Identification of specific etiologic agents is often lacking. In vitro and in vivo data suggest that enterotoxigenic Bacteroides fragilis (ETBF) may contribute to the burden of colonic inflammatory diarrheal disease. The study goal was to investigate the pathogenesis of ETBF diarrheal illnesses.

METHODS

We performed an observational study of children and adults with acute diarrheal illnesses in Dhaka, Bangladesh, from January 2004 through November 2005, to define the clinical presentation, intestinal inflammatory responses, and systemic and intestinal antibody responses to ETBF. Other enteric pathogens were also evaluated.

RESULTS

ETBF was identified to cause a clinical syndrome with marked abdominal pain and nonfebrile inflammatory diarrhea in both children (age, >1 year) and adults. Fecal leukocytes, lactoferrin, and proinflammatory cytokines (interleukin 8, tumor necrosis factor-alpha)-as well as B. fragilis toxin systemic antitoxin responses-increased rapidly in ETBF-infected patients. Evidence of intestinal inflammation often persisted for at least 3 weeks, despite antibiotic therapy.

CONCLUSIONS

ETBF infection is a newly recognized cause of inflammatory diarrhea in children and adults. Future studies are needed to evaluate the role of ETBF in persistent colonic inflammation and other morbid sequelae of acute diarrheal disease.

Prospective multicenter study evaluating fecal calprotectin in adult acute bacterial diarrhea

BACKGROUND

Every year, about 2.2 million deaths occur worldwide due to diarrhea. Reliable diagnosis of patients with acute infectious diarrhea remains a formidable challenge to the clinicians. This is the first study reporting use of fecal calprotectin in diagnosing acute diarrhea. The aim was to compare the diagnostic accuracy of fecal calprotectin, fecal lactoferrin, and guaiac-based fecal occult blood test in a diverse group of consecutive patients with acute diarrhea in which routine bacterial stool cultures and cytotoxins for Clostridium difficile were performed.

METHODS

This was a prospective case-control multicenter study from January 2004 until October 2007 in 2383 consecutive patients with acute diarrhea. They provided stool samples for performing cultures. Patients with positive cultures and an equal number of matched controls with negative cultures underwent fecal occult blood test and calprotectin and lactoferrin assays.

RESULTS

Calprotectin, lactoferrin, and fecal occult blood tests demonstrated sensitivity and specificity of 83% and 87%, 78% and 54%, and 38% and 85%, respectively, for diagnosing acute bacterial diarrhea.

CONCLUSIONS

Calprotectin showed high correlation with bacteriologically positive infectious diarrhea compared with lactoferrin and fecal occult blood test. It may potentially revolutionize management algorithm for patients with acute diarrhea. As a screening test, calprotectin can generate results within hours to support presumptive diagnosis of infectious diarrhea, which can decide suitability of stool samples for culture.

Is Fecal Leukocyte Test a good predictor of Clostridium difficile associated diarrhea?

Background

Fecal leukocyte test (FLT) is widely used to screen for invasive diarrheas including C. difficile associated diarrhea (CDAD), which account for more than 25 % of all antibiotic associated diarrhea.

Method

263 stool samples from patients with suspected CDAD were studied simultaneously for fecal leukocyte test (FLT) and Clostridium difficile toxin assay (CDTA). FLT was performed by the Giemsa technique and CDTA was performed by enzyme immuno assay (EIA).

Results

Sensitivity, specificity, positive predictive value and negative predictive value of FLT as compared to CDTA were 30%, 74.9%, 13.2% and 89.3% respectively.

Conclusion

Considering the poor sensitivity of FLT, and the comparable cost and time of obtaining a CDTA at our institution, we conclude that FLT is not a good screening test for CDAD. Possible reasons for FLT being a poor predictor of CDTA are discussed.

Single-dose quinolone treatment in acute gastroenteritis

BACKGROUND

Acute diarrhea is a common disease worldwide and in Israel, a Mediterranean country. Acute bacterial gastroenteritis (ABGE) is the leading cause of severe diarrhea in Israel in summer and early autumn. Although there are some reports showing some benefit from empiric antibiotic therapy in acute gastroenteritis, most are old reports using nondefinitive diagnostic criteria and using 5-day antibiotic regimens.

AIMS

1. To examine the efficiency of antibiotic therapy in relatively severe ABGE in general. 2. To check the efficiency of the different types of quinolones in the treatment of ABGE. 3. To compare various therapy regimens.

METHODS

All patients admitted to the Barzilai Medical Center emergency room during the period June to October in 2002-2004 who were defined by protocol as having relatively severe gastroenteritis and required hospitalization in the Department of Internal Medicine were included in the study. All were randomized either to a supportive treatment only group (STG) or to the antibiotic treatment group (ATG) of ofloxacin or levofloxacin with a single dose or BID for 5 days in addition to STGs. All patients were interviewed a week later about their medical history and duration of symptomatology.

RESULTS

One hundred thirty-nine patients were found eligible for the study in the above-mentioned period. Abdominal pain resolved 1.3 days earlier in the ATG in comparison to the STG whereas vomiting and diarrhea disappeared 1.0 and 0.8 days earlier, respectively, in the ATG versus the STG. In terms of fever abatement there was no difference between the regimens and no significant difference in symptomatology disappearance between various types of quinolones used or between the single antibiotic dose regimen and the 5-day antibiotic regimen groups.

CONCLUSIONS

1. Antibiotic therapy was found to shorten duration of symptoms in patients with relatively severe gastroenteritis. 2. Single-dose therapy is as effective and certainly significantly more cost effective in comparison to the 5-day antibiotic treatment regimen.

Rotavirus gastroenteritis

Rotavirus is the single most important cause of severe, dehydrating gastroenteritis in infants and young children worldwide. Rotavirus gastroenteritis is associated with high morbidity in developed countries and significant mortality in developing countries. Virtually all children are infected with rotavirus by 3 years of age. Fecal-oral transmission is the most likely route of virus spread. Group A serotype strains G1 through G4 account for more than 90% of rotavirus gastroenteritis in humans, with G1 being the predominant serotype. The virus preferentially infects the mature small-intestinal enterocytes. Rotavirus gastroenteritis is characterized by fever, vomiting, and diarrhea, with vomiting particularly prominent. Dehydration is a frequent complication because of the severity of the diarrhea and the associated vomiting. Rehydration and maintenance of proper fluid and electrolyte balance remain the mainstay of treatment. Hygienic measures have little effect on the reduction of rotavirus infection rates. The disease can be effectively controlled by universal rotavirus vaccination.

Tumor necrosis factor-alpha and interleukin-10 in viral and bacterial gastroenteritis in children

BACKGROUND

Gastroenteritis is a common cause of hospitalization and is associated with high morbidity in children. C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10) are primary mediators of inflammation, and have been implicated in many infectious and non-infectious inflammatory diseases. The main objective of this study was to identify serum markers in viral and bacterial gastroenteritis.

METHODS

Thirty-one patients admitted to a pediatric infection ward with gastroenteritis and definite pathogens were enrolled in the study: 17 patients had viral gastroenteritis and 14 bacterial gastroenteritis. Serum levels of TNF-alpha, IL-10 and CRP were measured in these 31 patients, and in a control group of 15 healthy children.

RESULTS

Serum concentrations of TNF-alpha and CRP were significantly greater in patients with bacterial gastroenteritis than in patients with viral gastroenteritis and healthy controls (p < 0.001). Concentrations of IL-10 were increased, but not significantly, in patients with viral or bacterial gastroenteritis (p = 0.577 vs controls). Regarding diagnosis, the measurement of TNF-alpha and CRP levels was 78.6% and 92.0% sensitive, respectively; and 88.2% and 58.8% specific, respectively.

CONCLUSION

Serum TNF-alpha concentration may be a useful marker for distinguishing between viral and bacterial gastroenteritis.

Performance assessment of the fecal leukocyte test for inpatients

Traditionally, fecal leukocyte testing detects large bowel inflammation or disruption, conditions that allow leukocytes into the stool. However, test usefulness with inpatients is unclear. Two hundred five inpatients who had undergone one to three tests were identified, and their FLT results were compared to their gastrointestinal disease diagnoses at time of discharge. A specificity of 92% for detecting intact colonic mucosae in inpatients was found.

Diagnostic accuracy of stool assays for inflammatory bacterial gastroenteritis in developed and resource-poor countries

Because acute bacterial gastroenteritis is often inflammatory, rapid stool assays that detect intestinal inflammation might be used to distinguish between bacterial and nonbacterial gastroenteritis. We performed meta-analyses to determine the discriminatory power, in developed and in resource-poor countries, of rapid stool assays that test for lactoferrin, fecal leukocytes, fecal erythrocytes, and occult blood. In developed countries, the area under the summary receiver operating characteristic curve (AUC/SROC) was 0.89 for fecal leukocytes and 0.81 for occult blood. In resource-poor countries, the AUC/SROC was 0.79 for lactoferrin, 0.72 for fecal leukocytes, 0.63 for occult blood, and 0.61 for fecal erythrocytes. In developed countries, positive and negative likelihood ratios (LR+ and LR-, respectively) for fecal leukocytes were 4.56 and 0.32 when a threshold of >5 cells/high-power field was used, compared with 2.94 and 0.6 in resource-poor countries; for lactoferrin, LR+ was 1.34 and LR- was 0.17 in resource-poor countries when the threshold was an agglutination rating of "+" and a dilution of 1:50. In developing countries, rapid stool assays performed poorly, whereas in developed countries, tests for fecal leukocytes, lactoferrin, and occult blood were moderately useful and could identify patients who were more likely to benefit from empirical antibiotic therapy.

Clinical evaluation and management of acute infectious diarrhea in adults

Acute infectious diarrhea is a major global health problem. Issues for the developed and developing regions of the world differ. Awareness of disease pathophysiology and epidemiology are essential, however, for clinical evaluation and management. The immense human and economic burden imposed by acute diarrhea illness can be addressed only by thoughtful strategies aimed at prevention as well as cost-efficient evaluation and treatment.

Fecal leukocyte stain has diagnostic value for outpatients but not inpatients

The methylene blue stain for fecal leukocytes (FL) is widely used as an adjunct to slower but more accurate tests of diarrheal etiology, such as stool culture (SCx) or toxin assays for Clostridium difficile. Prior studies investigating the utility of FL for predicting SCx and C. difficile toxin assay (CDTA) results did not evaluate the importance of inpatient versus outpatient status. We conducted a study of patients who submitted a stool specimen to the Stanford Hospital Microbiology Laboratory between May 1998 and April 1999. The results for stool specimens that were tested by FL and by a confirmatory test (either SCx or CDTA) were used to determine whether the FL method helped to predict the results of these tests. Of 797 stools that were tested by FL method and at least one confirmatory test, 502 stools were tested by CDTA, and 473 stools were cultured. The FL test was 14% sensitive and 90% specific for C. difficile with a diagnostic threshold of one white blood cell/high-power field (WBC/HPF). The overall likelihood ratio (LR) for a positive CDTA was 1.4 with a 95% confidence interval (CI) of 0. 5 to 3.7 (P = 0.5) and was similar among inpatients and outpatients. In contrast, the presence of >/=1 WBC/HPF was 52% sensitive and 88% specific for the 27 positive SCx results and helped to predict a positive SCx result (LR, 4.2; 95% CI, 2.7 to 6.5; P < 0.001). The sensitivity of >/=1 WBC/HPF was 57%, and its predictive value for SCx was higher among outpatients (outpatient LR, 5.0; 95% CI, 2.9 to 8.6; P < 0.001; inpatient LR, 1.9; 95% CI, 0.3 to 10.8; P = 0.5). Among inpatients, only 4 (1.5%) of the 273 SCx results were positive, and the presence of >/=1 WBC/HPF was insensitive (25%) and did not predict a positive SCx (LR, 1.9; 95% CI, 0.3 to 10.8; P = 0.5). When the data were reanalyzed using a diagnostic threshold of five WBC/HPF for FL, the predictive power of the FL method was similar. Thus, FL was of no value in predicting CDTA positivity, nor was it helpful in predicting SCx results for inpatients. Neither SCx nor the FL method should routinely be performed on samples from inpatients. Among outpatients, presence of FLs should suggest a bacterial diarrhea in clinically compatible cases.

Screening of patients with acute infectious diarrhoea: evaluation of clinical features, faecal microscopy, and faecal occult blood testing

BACKGROUND

For optimal management of acute infectious diarrhoeal diseases, it is necessary to utilize a screening process to distinguish between invasive and non-invasive diarrhoeas. The aim of this study was to compare the diagnostic utilities of clinical features, faecal microscopy (FM), and faecal occult blood testing (FOBT) in distinguishing invasive diarrhoeas from non-invasive ones.

METHODS

A total of 1008 patients with acute diarrhoea were evaluated. Rectal swabs were cultured for Salmonella, Shigella, and Vibrio species; rectal swabs from 109 of these patients were also examined for Campylobacter, enterotoxigenic Escherichia coli, and rotavirus species. Isolation of faecal enteropathogens served as the gold standard. FOBT was performed with a commercial modified guaiac test. Specificity, sensitivity, positive predictive value (PPV), negative predictive value (NPV), accuracy, and likelihood ratio were compared.

RESULTS

Among the 1008 patients 402 with a single identified enteropathogen were available for analysis. Invasive and non-invasive enteropathogens were isolated from 262 (65.2%) and 140 (34.8%) cases, respectively. The presence of visible blood in faeces was almost a pathognomonic sign of invasive diarrhoea but had poor sensitivity. Clinical features were useful but inadequate in differentiating patients with non-bloody diarrhoea (74% of patients) into invasive and non-invasive categories. The sensitivities, specificities, PPVs, and NPVs of FM and FOBT were 75%, 77%, 58%, 88%, and 85%, 68%, 53%, and 91%, respectively.

CONCLUSION

The presence of visible blood in faeces is a highly specific clinical feature of invasive diarrhoea but suffers from low sensitivity. In non-bloody diarrhoea FOBT is a valuable screening test and is comparable to FM, particularly when interpreted in the clinical context.

Acute gastroenteritis

Acute gastroenteritis represents a frequent cause of morbidity and mortality among children in the developing world as well as morbidity in the developed world. Despite the large number of potential etiologic agents, management of gastroenteritis is uniform and aimed to prevent the two major complications, dehydration and malnutrition. Current guidelines emphasize the use of oral rehydration and the early reintroduction of age-appropriate foods. These guidelines are reviewed here, the underlying principles discussed, and practical points provided.

Utility of a rapid fecal latex agglutination test detecting the neutrophil protein, lactoferrin, for diagnosing inflammatory causes of chronic diarrhea

OBJECTIVE

The utility of tests for fecal neutrophils in the setting of chronic diarrhea has not been established. The purpose of this study was to determine the causes of chronic diarrhea associated with fecal neutrophils.

METHODS

One fecal specimen from each of 10 normal subjects, 26 patients with known microscopic colitis, 13 with celiac sprue, eight with Crohn's disease, four with ulcerative colitis, and 103 with chronic diarrhea of unknown origin, as well as 10 fecal specimens from a patient with chronic nongranulomatous enterocolitis were analyzed blindly for the presence of a neutrophil granule protein called lactoferrin using a commercial latex agglutination kit. Diagnostic evaluation of the 103 patients with chronic diarrhea was carried out to determine the diagnostic accuracy of this test for chronic inflammatory bowel disease.

RESULTS

None of the normal control subjects, three of 39 patients with microscopic colitis or celiac sprue, all 10 specimens from the patient with enterocolitis, and all 12 control patients with ulcerative colitis or Crohn's disease had a positive fecal lactoferrin test. Eleven of 103 patients with chronic diarrhea presenting without a diagnosis had a positive test, and all were diagnosed with an inflammatory condition of the colon (five-, ulcerative colitis; four-, Crohn's disease; one-, ischemic colitis; and one-, microscopic colitis). Only one patient with inflammatory bowel disease had a negative lactoferrin test. The sensitivity, specificity, and positive and negative predictive values of the fecal lactoferrin test for ulcerative or Crohn's colitis were 90%, 98%, 82%, and 99%, respectively.

CONCLUSION

The major cause of fecal neutrophils in patients with chronic diarrhea is chronic inflammatory bowel disease of the colon. The latex agglutination test for fecal lactoferrin offers a highly sensitive, specific, and simple means for detection of fecal neutrophils in these patients.

Fecal lactoferrin, fecal leukocytes and occult blood in the diagnostic approach to childhood invasive diarrhea

OBJECTIVE

To compare fecal screening tests in the diagnostic approach to childhood invasive diarrhea.

SETTING AND PATIENTS

We assessed 125 consecutive children with acute diarrhea for fecal lactoferrin, fecal leukocytes and occult blood from November, 1995, to June, 1996.

RESULTS

Lactoferrin showed a greater overall sensitivity than fecal leukocytes or occult blood for detecting invasive pathogens. Combinations of lactoferrin or fecal leukocytes and of lactoferrin or occult blood or both yielded sensitivities and negative predictive values close to 100%, being superior to all other combinations. All patients with full breast-feeding and mixed feeding had a positive lactoferrin test with a 1:50 dilution used as the cutoff. In controls without diarrhea being exclusively bottle-fed, 3 of 15 (20%) still showed a positive lactoferrin result at the dilution of 1:50. This compared with 15 of 15 (100%) positive results among controls fully breast-fed, 14 of 15 (93%) among controls predominantly breast-fed and 11 of 15 (73%) among control children predominantly bottle-fed.

CONCLUSIONS

This study confirms the usefulness of lactoferrin testing as a negative predictor. Breast-feeding lowers the specificity of the test but does not alter the sensitivity. Fecal lactoferrin may be viewed as the screening test of choice to avoid expensive stool cultures in the diagnostic approach to invasive diarrhea.

Fecal screening tests in the approach to acute infectious diarrhea: a scientific overview

OBJECTIVE

To evaluate the value of fecal leukocytes, fecal occult blood, fecal lactoferrin and combination of fecal leukocytes with clinical data in the workup of patients with inflammatory diarrhea.

DATA IDENTIFICATION

A systematic literature search in all languages using MEDLINE (1970 to 1994), reference lists of articles primarily retrieved and of review articles and correspondence with experts in the field.

STUDY SELECTION

The search identified 2603 references, 81 of which were deemed relevant on the basis of prespecified selection criteria. Of these 25 contained sufficient data for further analysis and thus were finally included.

DATA EXTRACTION

All data from the selected articles were extracted by one observer whereas the second reviewer checked these data for accuracy. True positive rates and false positive rates were calculated from each 2 x 2 table.

RESULTS OF DATA ANALYSIS

The study summarizes the diagnostic accuracy of the signaled tests as predictors of inflammatory diarrhea as defined by stool culture (the reference test). Plots of true positive rates against false positive rates demonstrated widely scattered points, indicating heterogeneity. A summary receiver operating characteristic curve was fitted to the data with the use of logistic transforms and weighted least squares linear regression. Of the 25 studies analyzed 38 data points were used to construct summary receiver operating characteristic curves for index tests.

CONCLUSIONS

Fecal lactoferrin was the most accurate index test. Fecal leukocytes showed the lowest performance as assessed by the area under the curve. Occult blood and combination of fecal leukocytes with clinical data yielded intermediate curves. A limited number of studies (fecal lactoferrin, and fecal leukocytes with clinical data) and methodologic flaws identified in the assessed studies must be solved in future primary studies to improve the usefulness of the metaanalytic approach used here.

C-reactive protein in viral and bacterial gastroenteritis in childhood

To differentiate bacterial from viral infections the level of C-reactive protein in serum samples was studied in three groups of children under 5 years of age with gastroenteritis. Of the 53 children with bacterial infection, 41 (77%) had C-reactive protein levels > or = 12 mg1 -1, 32 (66%) > or = 20 mgl-1 and 24 (45%) > or = 35 mgl-1. Of the 35 patients with viral infection, 4 (11%) had C-reactive protein levels > or = 12 mgl-1, 3 (9%) > or = 20 mgl-1 and 1 (3%) > or = 35 mgl-1. The best balance between sensitivity and specificity of C-reactive protein was obtained for a cut-off level > or = 12 mgl-1 (sensitivity 77%, specificity 89%) as compared to > or = 20 mgl-1 (sensitivity 58%, specificity 97%) and > or = 35 mgl-1 (sensitivity 44%, specificity 97%). Our results suggest that the determination of C-reactive protein values may be a useful tool for predicting bacterial gastroenteritis in children.

Role of stool screening tests in diagnosis of inflammatory bacterial enteritis and in selection of specimens likely to yield invasive enteric pathogens

The Leuko-Test yielded a negative predictive value of 98.4% when it was used to screen 325 patients for inflammatory bacterial enteritis and a negative predictive value of 99.4% when it was used to screen 416 stool specimens for those from which enteric pathogens would likely be recovered when cultured. Neither microscopy for fecal leukocytes nor an assay for fecal occult blood, alone or in combination, allowed for the reliable detection of invasive bacterial enteritis or the reliable selection of specimens for culture. When positive in the Leuko-Test, specimens collected from patients after the third day of hospitalization did not yield enteric pathogens when the specimens were cultured, and specimens collected from inpatients within the first 3 days of hospitalization or from outpatients did not contain Clostridium difficile toxin A. As a screening test, the Leuko-Test has the ability to generate rapidly a result which can support the presumptive diagnosis of inflammatory bacterial enteritis or which can be used to determine the suitability of stool specimens for bacteriologic culture.

To culture or not to culture: fecal lactoferrin screening for inflammatory bacterial diarrhea

Because of its low yield in unselected specimens, stool culture is often cost ineffective. We tested 55 fecal samples from Fairfax Hospital (46 patients with diarrhea and 9 from controls without diarrhea) for lactoferrin by latex agglutination (LFLA) with the Leukotest (Techlab, Blacksburg, Va.) as a marker for inflammatory diarrhea. Of the 28 samples with Salmonella, Shigella, or Campylobacter infection, 93% had detectable fecal lactoferrin at > or = 1:50 (61% had LFLA titers of > or = 1:400), while 83% of 18 samples with rotavirus or no detectable pathogen were LFLA negative at a titer of 1:50 (100% were negative at 1:400). All 9 controls without diarrhea were LFLA negative at 1:50. The use of fecal lactoferrin to screen for inflammatory diarrhea selects specimens for which stool culture is fivefold more likely to yield an invasive bacterial pathogen (reducing the cost per positive result by over $800) and thus may greatly enhance a cost-effective approach to evaluating diarrheal illness.

Intestinal coinfection with numerous Giardia trophozoites and Vibrio cholerae in hospitalized children with watery diarrhea

During the recent cholera epidemic which affected Peru and other Latin American countries, fresh stool samples of 100 hospitalized children were assessed February through April 1991. The children had been admitted because of profuse watery diarrhea. The microbiologic study of wet mount preparations showed curved bacteria suspicious for cholera agent and confirmed afterward to be Vibrio cholerae 01 scrotype Inaba. In 30% of such cases, besides the curved bacteria, a strikingly large number of trophozoites of Giardia intestinalis were observed. The same samples studied by permanent stains confirmed the presence of Giardia trophozoites. To our knowledge, the association of Giardia with serious epidemic cholera infection has not been previously described. All patients were admitted because of severe dehydration requiring intravenous fluid replacement, which might suggest a synergistic role for the above-noted coinfection. Adequately designed case-control studies are needed to ascertain the frequency and the pathophysiologic and clinical significance of such an unusual association.

Salmonella, Shigella, and Campylobacter: common bacterial causes of infectious diarrhea

Salmonella, Shigella, and Campylobacter species are the most common causes of acute bacterial enteritis in the United States. These pathogens should be considered seriously in children who progress rapidly from secretory to inflammatory diarrhea syndrome or in whom diarrhea persists beyond 5 to 6 days. Furthermore, children who appear more toxic than their state of dehydration would suggest should be suspected of having an acute bacterial etiology for their diarrhea. Systemic, extraintestinal dissemination of these organisms is uncommon, with the exception of salmonella infection during the first year of life and in immunocompromised hosts. In this latter situation, culture of blood and other appropriate body fluids should be considered, along with empiric systemic antibiotic therapy. When antibiotics are warranted in patients with shigella or campylobacter infection, oral therapy is usually sufficient. Careful attention to handwashing and personal hygiene is always appropriate to prevent further spread of these organisms. The very low infectious dose of shigella infection mandates an even more compulsive attention to these latter recommendations when this organism is implicated.