The impact of Zika emergence in remote communities in northwestern Ecuador.

The Zika virus (ZIKV) epidemic in Latin America (2015-2016) has primarily been studied in urban centers, with less understanding of its impact on smaller rural communities. To address this gap, we analyzed ZIKV sero-epidemiology in six rural Ecuadorian communities (2018-2019) with varying access to a commercial hub. Seroprevalence ranged from 19% to 54% measured by NS1 blockade of binding ELISA. We observed a decline in ZIKV seroprevalence between 2018 and 2019 that was greater among younger populations, suggesting that the attack rates in the 2015-16 epidemic were significantly higher than our 2018 observations. These data indicate that the 2015-16 epidemic included significant transmission in rural and more remote settings. Our observations of high seroprevalence in our area of study highlights the importance of surveillance and research in rural areas lacking robust health systems to manage future Zika outbreaks and vaccine initiatives.

A Model-Based 13C-Sucrose Breath Test Diagnostic for Gut Function Disorders Characterized by a Loss of Sucrase-Isomaltase Enzymatic Activity.

BACKGROUND: Environmental enteric dysfunction (EED) causes malnutrition in children in low-resource settings. Stable-isotope breath tests have been proposed as noninvasive tests of altered nutrient metabolism and absorption in EED, but uncertainty over interpreting the breath curves has limited their use. The activity of sucrose-isomaltase, the glucosidase enzyme responsible for sucrose hydrolysis, may be reduced in EED. We previously developed a mechanistic model describing the dynamics of the 13C-sucrose breath test (13C-SBT) as a function of underlying metabolic processes. OBJECTIVES: This study aimed to determine which breath test curve dynamics are associated with sucrose hydrolysis and with the transport and metabolism of the fructose and glucose moieties and to propose and evaluate a model-based diagnostic for the loss of activity of sucrase-isomaltase. METHODS: We applied the mechanistic model to 2 sets of exploratory 13C-SBT experiments in healthy adult participants. First, 19 participants received differently labeled sucrose tracers (U-13C fructose, U-13C glucose, and U-13C sucrose) in a crossover study. Second, 16 participants received a sucrose tracer accompanied by 0, 100, and 750 mg of Reducose, a sucrase-isomaltase inhibitor. We evaluated a model-based diagnostic distinguishing between inhibitor concentrations using receiver operator curves, comparing with conventional statistics. RESULTS: Sucrose hydrolysis and the transport and metabolism of the fructose and glucose moieties were reflected in the same mechanistic process. The model distinguishes these processes from the fraction of tracer exhaled and an exponential metabolic process. The model-based diagnostic performed as well as the conventional summary statistics in distinguishing between no and low inhibition [area under the curve (AUC): 0.77 vs. 0.66-0.79] and for low vs. high inhibition (AUC 0.92 vs. 0.91-0.99). CONCLUSIONS: Current summary approaches to interpreting 13C breath test curves may be limited to identifying only gross gut dysfunction. A mechanistic model-based approach improved interpretation of breath test curves characterizing sucrose metabolism.

Short-term dynamics of linear growth among Peruvian infants in the first year of life in a population with linear growth faltering.

OBJECTIVES: Infant growth is recognized to vary over the short term, with periods of greater and lesser linear growth velocity. Our objectives were to (1) examine the potential differences in overall growth profiles between children who experienced cumulative growth faltering in the first year of life consistent with that seen by many children living in poverty in low- and middle-income countries, versus children without growth faltering and (2) test whether biological factors were associated with the timing of magnitude of growth saltations. METHODS: Thrice-weekly measurements of length were recorded for n = 61 Peruvian infants (28 boys and 33 girls) enrolled from birth to 1 year. A total of 6040 measurements were analyzed. We tested for the evidence of saltatory growth and used hurdle models to test whether the timing and magnitude of saltations varied between children with greater or lesser growth faltering. RESULTS: There were no differences in the duration of stasis periods or magnitude of growth saltations between children who were stunted at 1 year old (N = 18) versus those who were not stunted (N = 43). Children who experienced greater declines in LAZ in the first year of life trended toward longer periods between saltations than those with less of a decline (14.5 days vs. 13.4 days, p = .0512). A 1-unit increase in mid upper arm circumference for age Z-score in the 21 days prior was associated with 35% greater odds of a saltation occurring (p < .001), and a 0.128 cm greater saltation (p < .001). CONCLUSIONS: After characterizing infant growth into periods of saltation and stasis, our results suggest that increases in weight preceded increases in length.

Leukocyte telomere length predicts subsequent infectious morbidity among Colombian schoolchildren.

OBJECTIVE: Telomere length (TL) attrition is related to chronic disease risk. However, less is known on whether TL predicts infectious outcomes, especially in childhood. We examined whether leukocyte TL (LTL) was associated with subsequent infectious morbidity in schoolchildren. METHODS: We assessed LTL in 717 Colombian children 5-12 years-old at the beginning of a school year and followed them through the year for daily occurrence of common infection symptoms and doctor visits. We estimated adjusted incidence rate ratios (IRR) with 95% confidence intervals (CI) of gastrointestinal and respiratory syndromes for quartiles of standardized LTL Z score and per unit LTL Z score. RESULTS: A longer LTL was associated with increased incidence of all infectious morbidity syndromes considered. Adjusted IRR (95% CI) per unit LTL Z score were 1.55 (1.20, 2.00) for diarrhea with vomiting, 1.34 (1.13, 1.60) for cough with fever, 1.70 (1.28, 2.28) for ear infection, and 1.66 (1.36, 2.02) for doctor visits with symptoms. CONCLUSIONS: Longer LTL is related to increased incidence of common infectious morbidities in middle childhood.

Mechanistic inference of the metabolic rates underlying [Formula: see text]C breath test curves.

Carbon stable isotope breath tests offer new opportunities to better understand gastrointestinal function in health and disease. However, it is often not clear how to isolate information about a gastrointestinal or metabolic process of interest from a breath test curve, and it is generally unknown how well summary statistics from empirical curve fitting correlate with underlying biological rates. We developed a framework that can be used to make mechanistic inference about the metabolic rates underlying a 13C breath test curve, and we applied it to a pilot study of 13C-sucrose breath test in 20 healthy adults. Starting from a standard conceptual model of sucrose metabolism, we determined the structural and practical identifiability of the model, using algebra and profile likelihoods, respectively, and we used these results to develop a reduced, identifiable model as a function of a gamma-distributed process; a slower, rate-limiting process; and a scaling term related to the fraction of the substrate that is exhaled as opposed to sequestered or excreted through urine. We demonstrated how the identifiable model parameters impacted curve dynamics and how these parameters correlated with commonly used breath test summary measures. Our work develops a better understanding of how the underlying biological processes impact different aspect of 13C breath test curves, enhancing the clinical and research potential of these 13C breath tests.

Multiple burdens of malnutrition and relative remoteness in rural Ecuadorian communities.

OBJECTIVE: Social and economic changes associated with new roads can bring about rapid nutritional transitions. To study this process, we: (1) describe trends in adult overweight and obesity (OW/OB) among rural Afro-Ecuadorians over time and across a gradient of community remoteness from the nearest commercial centre; (2) examine the relationship between male and female adult OW/OB and factors associated with market integration such as changing livelihoods and (3) examine the co-occurrence of adult OW/OB and under-five stunting and anaemia. DESIGN: Adult anthropometry was collected through serial case-control studies repeated over a decade across twenty-eight communities. At the same time, anthropometry and Hb were measured for all children under 5 years of age in every community. SETTING: Northern coastal Ecuador. PARTICIPANTS: Adults (n 1665) and children under 5 years of age (n 2618). RESULTS: From 2003 and 2013, OW/OB increased from 25·1 % to 44·8 % among men and 59·9 % to 70·2 % among women. The inverse relationship between remoteness and OW/OB in men was attenuated when adjusting for urban employment, suggesting that livelihoods mediated the remoteness-OW/OB relationship. No such relationship was observed among women. Communities with a higher prevalence of male OW/OB also had a greater prevalence of stunting, but not anaemia, in children under 5 years of age. CONCLUSIONS: The association between male OW/OB and child stunting at the community level, but not the household level, suggests that changing food environments, rather than household- or individual-level factors, drove these trends. A closer examination of changing socio-economic structures and food environments in communities undergoing rapid development could help mitigate future public health burdens.

La Niña weather impacts dietary patterns and dietary diversity among children in the Peruvian Amazon.

OBJECTIVE: In 2011-2012, severe El Niño Southern Oscillation (ENSO) conditions (La Niña) led to massive flooding and temporarily displacement in the Peruvian Amazon. Our aims were to examine the impact of this ENSO exposure on child diets, in particular: (1) frequency of food consumption patterns, (2) the amount of food consumed (g/d), (3) dietary diversity (DD), (4) consumption of donated foods, among children aged 9-36 months living in the outskirts of City of Iquitos in the Amazonian Peru. DESIGN: This was a longitudinal study that used quantitative 24-h recall dietary data collection from children aged 9-36 months from 2010 to 2014 as part of the MAL-ED birth cohort study. SETTING: Iquitos, Loreto, Peru. PARTICIPANTS: Two hundred and fifty-two mother-child dyads. RESULTS: The frequency of grains, rice, dairy and sugar in meals reduced by 5-7 %, while the frequency of plantain in meals increased by 24 % after adjusting for covariates. ENSO exposure reduced girl's intake of plantains and sugar. Despite seasonal fluctuations in the availability of fruits, vegetables and fish, DD remained constant across seasons and as children aged. However, DD was significantly reduced under moderate La Niña conditions by 0·32 (P < 0·05) food groups. Adaptive social strategies such as consumption of donated foods were significantly higher among households with girls. CONCLUSIONS: This is the first empirical study to show differential effect of the ENSO on the dietary patterns of children, highlighting differences by gender. Public health nutrition programmes should be climate- and gender-sensitive in their efforts to safeguard the diets of vulnerable populations.

Knowledge, attitudes, and practices of cervical cancer prevention and pap smears in two low-income communities in Lima, Peru.

BACKGROUND: Cervical cancer is a leading cause of death among Peruvian women. Barriers at multiple levels impact effective screening and treatment, including a lack of knowledge about cervical cancer and how regular screening can reduce morbidity and mortality through earlier detection. The aim of this study is to assess knowledge, attitudes, and practices regarding cervical cancer and its prevention in the peri-urban communities of Oasis and Pampas in southern Lima, Peru that can be used to inform future campaigns about cervical cancer prevention. METHODS: A cross-sectional survey that included several open-ended questions was administered to women in Pampas and Oasis between 2015 and 2016 to evaluate the knowledge, attitudes, and practices regarding cervical cancer and Pap smears. RESULTS: In total, 224 women were interviewed. Knowledge about cervical cancer and Pap smears was high, and attitudes were predominantly positive among most participants. Most participants knew how often they should get Pap smears (89.7%), when to begin seeking screening (74.6%), knew the price of a Pap smear (61.9%), and felt Pap smears were important for their health (70.1%). About one third (29.5%) of premenopausal women reported receiving a Pap smear in the last year. However, open ended questions revealed some knowledge gaps around Pap smears, as well as some stigma associated to Human Papilloma Virus (HPV) infection. CONCLUSION: Although knowledge of cervical cancer prevention was generally high and perceptions were positive among women in peri-urban Peruvian communities, our findings revealed there is a need for education on HPV infection prevalence among sexually active individuals to reduce stigma. Future research should focus on exploring experiences with follow-up and treatment associated with abnormal Pap smears, as well as perspectives from health authorities and professionals about barriers in the early detection and treatment process for cervical cancer.

Influences on catch-up growth using relative versus absolute metrics: evidence from the MAL-ED cohort study.

BACKGROUND: Poor growth in early childhood has been considered irreversible after 2-3 years of age and has been associated with morbidity and mortality over the short-term and with poor economic and cognitive outcomes over the long-term. The MAL-ED cohort study was performed in eight low-income settings with the goal of evaluating relationships between the child's environment and experience (dietary, illness, and pathogen exposure, among others) and their growth and development. The goal of this analysis is to determine whether there are differences in the factors associated with growth from 24 to 60 months using two different metrics. METHODS: Across six MAL-ED sites, 942 children had anthropometry data at 24 and 60 months, as well as information about socioeconomic status, maternal height, gut permeability (lactulose-mannitol z-score (LMZ)), dietary intake from 9 to 24 months, and micronutrient status. Anthropometric changes were in height- or weight-for-age z-score (HAZ, WAZ), their absolute difference from the growth standard median (HAD (cm), WAD (kg)), as well as recovery from stunting/underweight. Outcomes were modeled using multivariate regression. RESULTS: At 24 months, almost half of the cohort was stunted (45%) and 21% were underweight. Among those who were stunted at 24 months (n = 426), 185 (43%) were no longer stunted at 60 months. Most children increased their HAZ from 24 to 60 months (81%), whereas fewer (33%) had positive changes in their HAD. Linear regression models indicate that girls improved less than boys from 24 to 60 months (HAZ: -0.21 (95% CI -0.27, -0.15); HAD: -0.75 (-1.07, -0.43)). Greater intestinal permeability (higher LMZ) at 0-24 months was associated with lower relative and absolute changes from 24 to 60 months (HAZ: -0.10 (-0.16, -0.04); HAD: -0.47 (-0.73, -0.21)). Maternal height (per 10 cm) was positively associated with changes (HAZ: 0.09 (0.03, 0.15); HAD: 0.45 (0.15, 0.75)). Similar relationships were identified for changes in WAZ and WAD. CONCLUSIONS: The study children demonstrated improved growth from 24 to 60 months of age, but only a subset had positive changes in HAD and WAD. The same environmental factors were associated with growth from 24 to 60 months regardless of metric used (change in HAZ or HAD, or WAZ and WAD).

Evolution of the Bacillus Calmette-Guerin Scar and Its Association with Birth and Pregnancy Characteristics in a Prospective Cohort of Infants in Iquitos, Peru.

BACKGROUND: Bacillus Calmette-Guerin (BCG) scar formation is considered a visual marker of vaccination and cell-mediated immune response. This study characterized the association between pregnancy and birth characteristics with BCG scar formation. STUDY DESIGN: Pregnant women were enrolled prospectively. Infants were followed up for the first 6 months of life, and the diameter of the BCG scar was recorded. Marginal models were fitted to assess the association of BCG scar diameter with pregnancy and birth characteristics using linear regressions with generalized estimating equations. RESULTS: A total of 307 infants were enrolled, of whom 19.2% (59/307) were of low birth weight. Among those with known gestational age, 7.1% were preterm births (21/295). Overall, 98.7% (303/307) of infants developed a BCG scar. BCG scar trends in a tropical environment, such as the Amazon, differ from the trends evidenced in the capital of Peru. For every additional week of gestational age, the mean scar diameter increased by 0.1 mm (95% confidence interval [CI]: 0.02, 0.24; p = 0.017). Maternal illness during pregnancy impacted BCG scar size, as the infants of mothers who self-report fever had a smaller scar diameter (1 mm, 95% CI: 0.5, 1.8 mm; p = 0.001). CONCLUSION: The immune reaction to the BCG vaccination is affected by gestational age at birth and systemic inflammatory episodes during pregnancy.

Small scale migration along the interoceanic highway in Madre de Dios, Peru: an exploration of community perceptions and dynamics due to migration.

BACKGROUND: Madre de Dios, a southern state in the Peruvian Amazon basin, has experienced rapid development as well as an influx of migrants since the construction of the Interoceanic Highway (IOH) connecting Brazil, Bolivia, and the Peruvian coast. We explored perceptions of migration and development in up to eight communities along the IOH in Madre de Dios following construction of the highway. METHODS: We conducted a multiple methods study involving focus group (FG) discussions and interviews with key informants (KIs) in eight communities in Madre de Dios. The data was used to develop and apply a survey on demographics, financial, personal, social, human, and physical capital in four communities between February 2014 and March 2015. RESULTS: We conducted 12 FGs and 34 KI interviews. A total of 522 people participated in the survey. Comparing migrants (those who had moved to the area after construction of the IOH) and non-migrants, we found no difference in food security or access to health services. The majority (67.6%) of respondents from both groups reported that illness was their primary threat to well-being. Non-migrants owned more land than migrants (p < 0.001), were more likely to have piped water directly in their home (p = 0.046), and were more likely to participate in community groups (p = 0.012). Looking at perceptions about migrants, KIs and FGs discussed both positive perceptions of migrants (increased cultural exchange and new technology) and negative perceptions (increased drugs and alcohol in their communities and a lack of investment in the community). Both migrants and non-migrants reported trusting the local government more than the national government. CONCLUSIONS: Although we hypothesized that migrants would have decreased access to food, water, health services, and land relative to non-migrants, our results show that the only significant differences were in land ownership and water access. Efforts to improve community infrastructure should be carried out at the local level and focus on improving issues reported by both groups, such as potable water, sewage, and increased access to health services. Furthermore, an emphasis on community cohesion, ensuring land rights, and increasing long-term job opportunities should help ease tensions between migrants and non-migrants.

Dynamics of Cough Frequency in Adults Undergoing Treatment for Pulmonary Tuberculosis.

Background: Cough is the major determinant of tuberculosis transmission. Despite this, there is a paucity of information regarding characteristics of cough frequency throughout the day and in response to tuberculosis therapy. Here we evaluate the circadian cycle of cough, cough frequency risk factors, and the impact of appropriate treatment on cough and bacillary load. Methods: We prospectively evaluated human immunodeficiency virus-negative adults (n = 64) with a new diagnosis of culture-proven, drug-susceptible pulmonary tuberculosis immediately prior to treatment and repeatedly until treatment day 62. At each time point, participant cough was recorded (n = 670) and analyzed using the Cayetano Cough Monitor. Consecutive coughs at least 2 seconds apart were counted as separate cough episodes. Sputum samples (n = 426) were tested with microscopic-observation drug susceptibility broth culture, and in culture-positive samples (n = 252), the time to culture positivity was used to estimate bacillary load. Results: The highest cough frequency occurred from 1 pm to 2 pm, and the lowest from 1 am to 2 am (2.4 vs 1.1 cough episodes/hour, respectively). Cough frequency was higher among participants who had higher sputum bacillary load (P < .01). Pretreatment median cough episodes/hour was 2.3 (interquartile range [IQR], 1.2-4.1), which at 14 treatment days decreased to 0.48 (IQR, 0.0-1.4) and at the end of the study decreased to 0.18 (IQR, 0.0-0.59) (both reductions P < .001). By 14 treatment days, the probability of culture conversion was 29% (95% confidence interval, 19%-41%). Conclusions: Coughs were most frequent during daytime. Two weeks of appropriate treatment significantly reduced cough frequency and resulted in one-third of participants achieving culture conversion. Thus, treatment by 2 weeks considerably diminishes, but does not eliminate, the potential for airborne tuberculosis transmission.

Age and Sex Normalization of Intestinal Permeability Measures for the Improved Assessment of Enteropathy in Infancy and Early Childhood: Results From the MAL-ED Study.

OBJECTIVES: The aim of the study was to describe changes in intestinal permeability in early childhood in diverse epidemiologic settings. METHODS: In a birth cohort study, the lactulose:mannitol (L:M) test was administered to 1980 children at 4 time points in the first 24 months of life in 8 countries. Data from the Brazil site with an incidence of diarrhea similar to that seen in the United States and no growth faltering was used as an internal study reference to derive age- and sex-specific z scores for mannitol and lactulose recoveries and the L:M ratio. RESULTS: A total of 6602 tests demonstrated mannitol recovery, lactulose recovery, and the L:M ratio were associated with country, sex, and age. There was heterogeneity in the recovery of both probes between sites with mean mannitol recovery ranging for 1.34% to 5.88%, lactulose recovery of 0.19% to 0.58%, and L:M ratios 0.10 to 0.17 in boys of 3 months of age across different sites. We observed strong sex-specific differences in both mannitol and lactulose recovery, with boys having higher recovery of both probes. Alterations in intestinal barrier function increased in most sites from 3 to 9 months of age and plateaued or diminished from 9 to 15 months of age. CONCLUSIONS: Alterations in recovery of the probes differ markedly in different epidemiologic contexts in children living in the developing world. The rate of change in the L:M-z ratio was most rapid and consistently disparate from the reference standard in the period between 6 and 9 months of age, suggesting that this is a critical period of physiologic impact of enteropathy in these populations.

A Comparison of Diarrheal Severity Scores in the MAL-ED Multisite Community-Based Cohort Study.

OBJECTIVES: There is a lack of consensus on how to measure diarrheal severity. Within the context of a multisite, prospective cohort study, we evaluated the performance of a modified Vesikari score (MAL-ED), 2 previously published scores (Clark and CODA [a diarrheal severity score (Community DiarrheA) published by Lee et al]), and a modified definition of moderate-to-severe diarrhea (MSD) based on dysentery and health care worker diagnosed dehydration. METHODS: Scores were built using maternally reported symptoms or fieldworker-reported clinical signs obtained during the first 7 days of a diarrheal episode. The association between these and the risk of hospitalization were tested using receiver operating characteristic analysis. Severity scores were also related to illness etiology, and the likelihood of the episode subsequently becoming prolonged or persistent. RESULTS: Of 10,159 episodes from 1681 children, 143 (4.0%) resulted in hospitalization. The area under the curve of each score as a predictor of hospitalization was 0.84 (95% confidence interval: 0.81, 0.87) (Clark), 0.85 (0.82, 0.88) (MAL-ED), and 0.87 (0.84, 0.89) (CODA). Severity was also associated with etiology and episode duration. Although families were more likely to seek care for severe diarrhea, approximately half of severe cases never reached the health system. CONCLUSIONS: Community-based diarrheal severity scores are predictive of relevant child health outcomes. Because they require no assumptions about health care access or utilization, they are useful in refining estimates of the burden of diarrheal disease, in estimating the effect of disease control interventions, and in triaging children for referral in low- and middle-income countries in which the rates of morbidity and mortality after diarrhea remain high.

Early child health in an informal settlement in the Peruvian Amazon.

BACKGROUND: Informal settlements are common throughout the developing world. In Peru, land occupations, commonly "invasions" in Spanish, are a means by which the extremely poor attempt to obtain access to land. Here, we examine difference in child health between two communities in the Peruvian Amazon, one well-established and one newly formed by 'invasion', as captured incidentally by a prospective epidemiological cohort study. METHODS: Between 2002 and 2006 a study designed to describe the epidemiology of pediatric enteric infections and child growth in a community-based setting enrolled 442 children in Santa Clara de Nanay, a community adjacent to the city of Iquitos, in Loreto, Peru. In early 2003, a land occupation, commonly called an "invasion" in Spanish, was organized by members of the Santa Clara community, and approximately 20 % of participating study families began occupying privately owned agricultural land adjacent to Santa Clara, thus forming the new community of La Union. RESULTS: Parents in families that chose to invade reported less education than parents in families that chose not to. Children in the new community experienced a higher incidence of diarrheal disease and non-specific fevers, although fewer helminth infections, than children who remained in the established community. At the time of the invasion, there were no differences in anthropometric status between the two groups; however children in the new community experienced greater progressive growth faltering over the course of the longitudinal study. CONCLUSIONS: Growth faltering in early childhood represents an enduring loss of human potential. Therefore, our data suggests the human cost of land invasion may be disproportionately borne by the youngest individuals. Innovative policy strategies may be needed to protect this vulnerable group.

How multiple episodes of exclusive breastfeeding impact estimates of exclusive breastfeeding duration: report from the eight-site MAL-ED birth cohort study.

The duration of exclusive breastfeeding (EBF) is often defined as the time from birth to the first non-breast milk food/liquid fed (EBFLONG), or it is estimated by calculating the proportion of women at a given infant age who EBF in the previous 24 h (EBFDHS). Others have measured the total days or personal prevalence of EBF (EBFPREV), recognizing that although non-EBF days may occur, EBF can be re-initiated for extended periods. We compared breastfeeding metrics in the MAL-ED study; infants' breastfeeding trajectories were characterized from enrollment (median 7 days, IQR: 4, 12) to 180 days at eight sites. During twice-weekly surveillance, caretakers were queried about infant feeding the prior day. Overall, 101 833 visits and 356 764 child days of data were collected from 1957 infants. Median duration of EBFLONG was 33 days (95% CI: 32-36), compared to 49 days based on the EBFDHS. Median EBFPREV was 66 days (95% CI: 62-70). Differences were because of the return to EBF after a non-EBF period. The median number of returns to EBF was 2 (IQR: 1, 3). When mothers re-initiated EBF (second episode), infants gained an additional 18.8 days (SD: 25.1) of EBF, and gained 13.7 days (SD: 18.1) (third episode). In settings where women report short gaps in EBF, programmes should work with women to return to EBF. Interventions could positively influence the duration of these additional periods of EBF and their quantification should be considered in impact evaluation studies. © 2016 John Wiley & Sons Ltd.

Lactulose: mannitol diagnostic test by HPLC and LC-MSMS platforms: considerations for field studies of intestinal barrier function and environmental enteropathy.

OBJECTIVES: The lactulose:mannitol (L:M) diagnostic test is frequently used in field studies of environmental enteropathy (EE); however, heterogeneity in test administration and disaccharide measurement has limited the comparison of results between studies and populations. We aim to assess the agreement between L:M measurement between high-performance liquid chromatography with pulsed amperometric detection (HPLC-PAD) and liquid chromatography-tandem mass spectrometry (LC-MSMS) platforms. METHODS: The L:M test was administered in a cohort of Peruvian infants considered at risk for EE. A total of 100 samples were tested for lactulose and mannitol at 3 independent laboratories: 1 running an HPLC-PAD platform and 2 running LC-MSMS platforms. Agreement between the platforms was estimated. RESULTS: The Spearman correlation between the 2 LC-MSMS platforms was high (ρ ≥ 0.89) for mannitol, lactulose, and the L:M ratio. The correlation between the HPLC-PAD platform and LC-MSMS platform was ρ = 0.95 for mannitol, ρ = 0.70 for lactulose, and ρ = 0.43 for the L:M ratio. In addition, the HPLC-PAD platform overestimated the lowest disaccharide concentrations to the greatest degree. CONCLUSIONS: Given the large analyte concentration range, the improved accuracy of LC-MSMS has important consequences for the assessment of lactulose and mannitol following oral administration in populations at risk for EE. We recommend that researchers wishing to implement a dual-sugar test as part of a study of EE use an LC-MSMS platform to optimize the accuracy of results and increase comparability between studies.

The development and validation of a survey to measure fecal-oral child exposure to zoonotic enteropathogens: The FECEZ Enteropathogens Index.

Child exposure to animal feces and associated enteropathogens contribute to a significant burden of disease in low- and middle-income countries. However, there are no standardized, validated survey-based approaches to enable accurate assessment of child exposure to zoonotic enteropathogens. We developed and validated a survey-based measure of exposure, the fecal-oral child exposure to zoonotic enteropathogens Index (the FECEZ Enteropathogens Index). First, we identified critical attributes of child exposure through in-depth interviews (IDIs) in Ecuador among individuals who care for animals (n = 29) and mothers of children under two years old (n = 58), and through a systematic review of existing exposure measures. Second, based on these findings, we developed a 105-question survey and administered it to 297 mothers with children under age five. Third, we refined the survey, using principal component analysis to determine the optimal number of components. The final index consisted of 34 items across two sub-domains: the child Environment and child Behavior. Lastly, we compared index scores to two commonly used, unvalidated measures of child exposure-maternal reported household animal ownership and presence of animal feces. Using the FECEZ Enteropathogens Index revealed varying degrees of exposure in our study population, with only two children having no exposure. In contrast, if we had used animal ownership or the presence of animal feces as a measure of exposure, 44% and 33% of children would have been classified as having no exposure, respectively. These common binary exposure measures may be inadequate because they do not provide sufficient information to identify the relative risk of zoonotic pathogen exposure. The FECEZ Enteropathogens Index overcomes this limitation, advancing our ability to assess exposure by quantifying the multiple components of child exposure to zoonotic enteropathogens with higher resolution. Additional testing and evaluation of the index is needed to ensure its reliability, validity, and cross-cultural equivalence in other contexts.

Performance of empirical and model-based classifiers for detecting sucrase-isomaltase inhibition using the13C-sucrose breath test.

The13C-sucrose breath test (13C-SBT) has been proposed to estimate sucrase-isomaltase (SIM) activity and is a promising test for SIM deficiency, which can cause gastrointestinal symptoms, and for intestinal mucosal damage caused by gut dysfunction or chemotherapy. We previously showed how various summary measures of the13C-SBT breath curve reflect SIM inhibition. However, it is uncertain how the performance of these classifiers is affected by test duration. We leveraged13C-SBT data from a cross-over study in 16 adults who received 0, 100, and 750 mg of Reducose, an SIM inhibitor. We evaluated the performance of a pharmacokinetic-model-based classifier,ρ, and three empirical classifiers (cumulative percent dose recovered at 90 min (cPDR90), time to 50% dose recovered, and time to peak dose recovery rate), as a function of test duration using receiver operating characteristic (ROC) curves. We also assessed the sensitivity, specificity, and accuracy of consensus classifiers. Test durations of less than 2 h generally failed to accurately predict later breath curve dynamics. The cPDR90 classifier had the highest ROC area-under-the-curve and, by design, was robust to shorter test durations. For detecting mild SIM inhibition,ρhad a higher sensitivity. We recommend13C-SBT tests run for at least a 2 h duration. Although cPDR90 was the classifier with highest accuracy and robustness to test duration in this application, concerns remain about its sensitivity to misspecification of the CO2production rate. More research is needed to assess these classifiers in target populations.

Performance of empirical and model-based classifiers for detecting sucrase-isomaltase inhibition using the 13 C-sucrose breath test.

Background: Environmental enteric dysfunction (EED) is a syndrome characterized by epithelial damage including blunting of the small intestinal villi and altered digestive and absorptive capacity which may negatively impact linear growth in children. The 13 C-sucrose breath test ( 13 C-SBT) has been proposed to estimate sucrase-isomaltase (SIM) activity, which is thought to be reduced in EED. We previously showed how various summary measures of the 13 C-SBT breath curve reflect SIM inhibition. However, it is uncertain how the performance of these classifiers is affected by test duration. Methods: We leveraged SBT data from a cross-over study in 16 adults who received 0, 100, and 750 mg of Reducose, a natural SIM inhibitor. We evaluated the performance of a pharmacokinetic-model-based classifier, ρ , and three empirical classifiers (cumulative percent dose recovered at 90 minutes (cPDR90), time to 50% dose recovered, and time to peak dose recovery rate), as a function of test duration using receiver operating characteristic curves. We also assessed the sensitivity, specificity, and accuracy of consensus classifiers. Results: Test durations of less than 2 hours generally failed to accurately predict later breath curve dynamics. The cPDR90 classifier had the highest area-under-the-curve and, by design, was robust to shorter test durations. For detecting mild SIM inhibition, ρ had a higher sensitivity. Conclusions: We recommend SBT tests run for at least a 2-hour duration. Although cPDR90 was the classifier with highest accuracy and robustness to test duration in this application, concerns remain about its sensitivity to misspecification of CO 2 production rate. More research is needed to assess these classifiers in target populations.