Tobias Chirwa | University of the Witwatersrand (original) (raw)

Papers by Tobias Chirwa

British Association of Perinatal Medicine and Neonatal Society, Jun 19, 2023

International Scholarly Research Notices, Aug 1, 2017

Background. The Bayley Scales of Infant and Toddler Development (III) is a tool developed in a We... more Background. The Bayley Scales of Infant and Toddler Development (III) is a tool developed in a Western setting. Aim. To evaluate the development of a group of inner city children in South Africa with no neonatal risk factors using the Bayley Scales of Infant and Toddler Development (III), to determine an appropriate cutoff to define developmental delay, and to establish variation in scores done in the same children before and after one year of age. Methods. Cohort follow-up study. Results. 74 children had at least one Bayley III assessment at a mean age of 19.4 months (95% CI 18.4 to 20.4). The mean composite cognitive score was 92.2 (95% CI 89.4 to 95.0), the mean composite language score was 94.8 (95% CI 92.5 to 97.1), and mean composite motor score was 98.8 (95% CI 96.8 to 101.0). No child had developmental delay using a cutoff score of 70. In paired assessments above and below one year of age, the cognitive score remained unchanged, the language score decreased significantly (= 0.001), and motor score increased significantly (= 0.004) between the two ages. Conclusion. The Bayley Scales of Infant and Toddler Development (III) is a suitable tool for assessing development in urban children in southern Africa.

BMC Pediatrics, May 6, 2010

Background: Audit of disease and mortality patterns provides essential information for health bud... more Background: Audit of disease and mortality patterns provides essential information for health budgeting and planning, as well as a benchmark for comparison. Neonatal mortality accounts for about 1/3 of deaths < 5 years of age and very low birth weight (VLBW) mortality for approximately 1/3 of neonatal mortality. Intervention programs must be based on reliable statistics applicable to the local setting; First World data cannot be used in a Third World setting. Many neonatal units participate in the Vermont Oxford Network (VON); limited resources prevent a significant number of large neonatal units from developing countries taking part, hence data from such units is lacking. The purpose of this study was to provide reliable, recent statistics relevant to a developing African country, useful for guiding neonatal interventions in that setting. Methods: This was a retrospective chart review of 474 VLBW infants admitted within 24 hours of birth, between 1 July 2006 and 30 June 2007, to the neonatal unit of Charlotte Maxeke Johannesburg Academic Hospital (CMJAH) in Johannesburg, South Africa. Binary outcome logistic regression on individual variables and multiple logistic regression was done to identify those factors determining survival. Results: Overall survival was 70.5%. Survival of infants below 1001 grams birth weight was 34.9% compared to 85.8% for those between 1001 and 1500 grams at birth. The main determinant of survival was birth weight with an adjusted survival odds ratio of 23.44 (95% CI: 11.22-49.00) for babies weighing between 1001 and 1500 grams compared to those weighing below 1001 grams. Other predictors of survival were gender (OR 3. 21; 95% CI 1.6-6.3), birth before arrival at the hospital (BBA) (OR 0.23; 95% CI: 0.08-0.69), necrotising enterocolitis (NEC) (OR 0.06; 95% CI: 0.02-0.20), hypotension (OR 0.05; 95% CI 0.01-0.21) and nasal continuous positive airways pressure (NCPAP) (OR 4.58; 95% CI 1.58-13.31). Conclusions: Survival rates compare favourably with other developing countries, but can be improved; especially in infants < 1001 grams birth weight. Resources need to be allocated to preventing the birth of VLBW babies outside hospital, early neonatal resuscitation, provision of NCPAP and prevention of NEC.

Annual review of statistics and its application, Mar 10, 2023

Several major global challenges, including climate change and water scarcity, warrant a scientifi... more Several major global challenges, including climate change and water scarcity, warrant a scientific approach to generating solutions. Developing high quality and robust capacity in (bio)statistics is key to ensuring sound scientific solutions to these challenges, so collaboration between academic and research institutes should be high on university agendas. To strengthen capacity in the developing world, South–North partnerships should be a priority. The ideas and examples of statistical capacity-building presented in this article are the result of several monthly online discussions between a mixedgroup of authors having international experience and formal links with Hasselt University in Belgium. The discussion focuses on statistical capacity-building through education (teaching), research, and societal impact. We have adopted an example-based approach, and in view of the background of the authors, the examples refer mainly to biostatistical capacity-building. Although many universities worldwide have already initiated university collaborations for development, we hope and believe that our ideas and concrete examples can serve as inspiration to further strengthen South–North partnerships on statistical capacity-building.

Journal of pediatric rehabilitation medicine, 2011

Hip movement pain was identified in 13 (32.5%) of 40 children and young adults with cerebral pals... more Hip movement pain was identified in 13 (32.5%) of 40 children and young adults with cerebral palsy who were in residential care. All of the participants were non-ambulatory (Level IV and V of the GMFCS), and their ages ranged from 8 to 26 years (median 16.5 years). Ten of the 13 participants had unilateral hip dislocation and three had bilateral dislocations. Degenerative hip changes were identified on radiographs of the painful dislocated hips. The occurrence of pain during a daily episode of washing, dressing, and transfer was recorded using non-verbal indicators. Washing of the lower body elicited significantly more pain responses than dressing (p=0.008) and transfer (p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001). None of the participants had daily pain during all of the care activities. Pain was present in 1/3 of the patients and was intermittent in nature, indicating that conservative management can be considered for persons with cerebral palsy at Levels IV and V of the GMFCS who have established hip dislocations and this type of pain. This management could include medication, attention to seating and positioning, and careful handling during daily care activities.

BMJ Paediatrics Open, Aug 1, 2017

Objectives The study aimed to compare the developmental outcome of very low birth weight infants ... more Objectives The study aimed to compare the developmental outcome of very low birth weight infants with a group of normal-term controls in a tertiary hospital in sub-Saharan Africa. Design A group of 105 very low birth weight infants were assessed at a mean age of 17.6 months (95% CI 16.7 to 18.6) using the Bayley Scales of Infant Development, Third Edition, and compared with a group of normal-term controls at the same mean age. results Seven of the study infants (7%) had developmental delay (a score below 70), compared with none in the control group (p=0.04). Three of the seven study infants were delayed on all three subscales, one of whom had cerebral palsy. A further 34% of the study infants were 'at risk' of developmental delay (a score below 85). There was no difference in the mean composite score between the study group and controls for the cognitive (p=0.56), motor (p=0.57) or language (p=0.66) subscales. There was no difference in mean composite scores on all subscales between infants who were appropriate for gestational age and those who were small for gestational age. Cognitive and motor scores remained stable in paired assessments of study infants before and after 1 year of age; language scores decreased significantly (p<0.001). Mechanical ventilation was the only risk factor significantly associated with a cognitive score below 85 in study infants. conclusion Very low birth weight infants in sub-Saharan Africa are at risk of developmental delay and require longterm neurodevelopmental follow-up.

BMC Infectious Diseases, Aug 22, 2016

Background: We investigated the prevalence of human papillomavirus (HPV) infection and associated... more Background: We investigated the prevalence of human papillomavirus (HPV) infection and associated behavioural risk factors in men-who-have-sex-with-men (MSM) attending a clinical service in Cape Town, South Africa. Methods: MSM were enrolled at the Ivan Toms Centre for Men's Health in Cape Town. A psychosocial and sexual behavioral risk questionnaire was completed for each participant and urine, oro-pharyngeal and anal swabs were collected for HPV testing using the Linear Array HPV Genotyping Test. Logistic regression analyses were performed to determine sexual risk factors associated with HPV infection at the three anatomical sites. Results: The median age of all 200 participants was 32 years (IQR 26-39.5), of which 31.0 % were black, 31.5 % mixed race/coloured and 35.5 % white. The majority of the participants (73.0 %) had completed high school, 42.0 % had a tertiary level qualification and 69.0 % were employed. HPV genotypes were detected in 72.8 % [95 % CI: 65. 9-79.0 %], 11.5 % [95 % CI: 7.4-16.8 %] and 15.3 % [95 % CI: 10.5-21.2 %] of anal, oro-pharyngeal and urine specimens, respectively. Prevalence of high-risk (HR)-HPV types was 57.6 % [95 % CI: 50.3-64.7 %] in anal samples, 7.5 % [95 % CI: 4.3-12.1 %] in oro-pharyngeal samples and 7.9 % [95 % CI: 4.5-12.7 %] in urine, with HPV-16 being the most common HR-HPV type detected at all sites. HPV-6/11/16/18 was detected in 40.3 % [95 % CI: 33.3-47.6 %], 4.5 % [95 % CI: 2.1-8.4 %] and 3.2 % [95 % CI: 1.2-6.8 %] of anal, oro-pharyngeal and urine samples, respectively. Multiple HPV types were more common in the anal canal of MSM while single HPV types constituted the majority of HPV infections in the oropharynx and urine. Among the 88 MSM (44.0 %) that were HIV positive, 91.8 % [95 % CI: 83.8-96.6 %] had an anal HPV infection, 81.2 % [95 % CI: 71.2-88.8 %] had anal HR-HPV and 85.9 % [95 % CI: 76.6-92.5 %] had multiple anal HPV types. Having sex with men only, engaging in group sex in lifetime, living with HIV and practising receptive anal intercourse were the only factors independently associated with having any anal HPV infection. Conclusions: Anal HPV infections were common among MSM in Cape Town with the highest HPV burden among HIV co-infected MSM, men who have sex with men only and those that practiced receptive anal intercourse. Behavioural intervention strategies and the possible roll-out of HPV vaccines among all boys are urgently needed to address the high prevalence of HPV and HIV co-infections among MSM in South Africa.

BMC Pediatrics, Feb 1, 2012

Background: Advances in neonatal care allow survival of extremely premature infants, who are at r... more Background: Advances in neonatal care allow survival of extremely premature infants, who are at risk of handicap. Neurodevelopmental follow up of these infants is an essential part of ongoing evaluation of neonatal care. The neonatal care in resource limited developing countries is very different to that in first world settings. Follow up data from developing countries is essential; it is not appropriate to extrapolate data from units in developed countries. This study provides follow up data on a population of very low birth weight (VLBW) infants in Johannesburg, South Africa. Methods: The study sample included all VLBW infants born between 01/06/2006 and 28/02/2007 and discharged from the neonatal unit at Charlotte Maxeke Johannesburg Academic Hospital (CMJAH). Bayley Scales of Infant and Toddler Development Version 111 (BSID) 111 were done to assess development. Regression analysis was done to determine factors associated with poor outcome. Results: 178 infants were discharged, 26 were not available for follow up, 9 of the remaining 152 (5.9%) died before an assessment was done; 106 of the remaining 143 (74.1%) had a BSID 111 assessment. These 106 patients form the study sample; mean birth weight and mean gestational age was 1182 grams (SD: 197.78) and 30.81 weeks (SD: 2.67) respectively. The BSID (111) was done at a median age of 16.48 months. The mean cognitive subscale was 88.6 (95% CI: 85.69-91.59), 9 (8.5%) were < 70, mean language subscale was 87.71 (95% CI: 84.85-90.56), 10 (9.4%) < 70, and mean motor subscale was 90.05 (95% CI: 87.0-93.11), 8 (7.6%) < 70. Approximately one third of infants were identified as being at risk (score between 70 and 85) on each subscale. Cerebral palsy was diagnosed in 4 (3.7%) of babies. Factors associated with poor outcome included cystic periventricular leukomalacia (PVL), resuscitation at birth, maternal parity, prolonged hospitalisation and duration of supplemental oxygen. PVL was associated with poor outcome on all three subscales. Birth weight and gestational age were not predictive of neurodevelopmental outcome. Conclusion: Although the neurodevelopmental outcome of this group of VLBW infants was within the normal range, with a low incidence of cerebral palsy, these results may reflect the low survival of babies with a birth weight below 900 grams. In addition, mean subscale scores were low and one third of the babies were identified as "at risk", indicating that this group of babies warrants long-term follow up into school going age.

BMJ Open, Apr 1, 2022

Figure 3 Impact of outcomes in a multiphase trial and intervention components. CHWs, community he... more Figure 3 Impact of outcomes in a multiphase trial and intervention components. CHWs, community health workers.

PLoS ONE, 2022

Background In drug trials, adverse events (AEs) burden can induce treatment non-adherence or disc... more Background In drug trials, adverse events (AEs) burden can induce treatment non-adherence or discontinuation. The non-adherence and discontinuation induce selection bias, affecting drug safety interpretation. Nested case-control (NCC) study can efficiently quantify the impact of the AEs, although choice of sampling approach is challenging. We investigated whether NCC study with incidence density sampling is more efficient than NCC with path sampling under conditional logistic or weighted Cox models in assessing the effect of AEs on treatment non-adherence and participation in preventive antimalarial drug during pregnancy trial. Methods Using data from a trial of medication to prevent malaria in pregnancy that randomized 600 women to receive chloroquine or sulfadoxine-pyrimethamine during pregnancy, we conducted a NCC study assessing the role of prospectively collected AEs, as exposure of interest, on treatment non-adherence and study non-completion. We compared estimates from NCC st...

Research Square (Research Square), Apr 1, 2021

Background In drug trials, clinical adverse events (AEs), concomitant medication and laboratory s... more Background In drug trials, clinical adverse events (AEs), concomitant medication and laboratory safety outcomes are repeatedly collected to support drug safety evidence. Despite the potential correlation of these outcomes, they are typically analysed separately, potentially leading to misinformation and inefficient estimates due to partial assessment of safety data. Using joint modelling, we investigated whether clinical AEs vary by treatment and how laboratory outcomes (alanine amino-transferase, total bilirubin) and concomitant medication are associated with clinical AEs over time following artemisinin-based antimalarial therapy. Methods We used data from a trial of artemisinin-based treatments for malaria during pregnancy that randomized 870 women to receive artemether-lumefantrine (AL), amodiaquine-artesunate (ASAQ) and dihydroartemisinin-piperaquine (DHAPQ). We fitted a joint model containing four sub-models from four outcomes: longitudinal sub-model for alanine aminotransferase, longitudinal sub-model for total bilirubin, Poisson sub-model for concomitant medication and Poisson sub-model for clinical AEs. Since the clinical AEs was our primary outcome, the longitudinal sub-models and concomitant medication sub-model were linked to the clinical AEs sub-model via current value and random effects association structures respectively. We fitted a conventional Poisson model for clinical AEs to assess if the effect of treatment on clinical AEs (i.e. incidence rate ratio (IRR)) estimates differed between the conventional Poisson and the joint models, where AL was reference treatment.

Objectives To investigate the distribution of human papillomavirus (HPV) genotypes and determine ... more Objectives To investigate the distribution of human papillomavirus (HPV) genotypes and determine the associations between HPV infection and HIV coinfection in sexually active heterosexual men with anogenital warts (GW), male urethral discharge or asymptomatic men. Methods Valid specimens for HPV genotyping were obtained from three patient groups consisting of 108 men with GW, 56 men with urethral discharge syndrome and 50 asymptomatic men attending for HIV voluntary counselling and testing. The Linear Array HPV Genotyping Test was used to determine the HPV genotype distribution among study participants. Sera were tested for HIV antibodies using two commercial rapid tests. Results The prevalence of anogenital HPV among study participants was 78% (166). HPV DNA was detected in 100% (108) of GW, 48% (27) of men with urethral discharge syndrome and 62% (31) of voluntary counselling and testing participants. HPV types 6, 11, 16 and 18 were prevalent as either single or combined infections in 81% (134) of all HPV-positive study participants. HPV types 6 and/or 11 were significantly higher among GW patients (p<0.001). After adjusting for patient groups, HIV seropositivity was significantly associated with multiple HPV infections (OR¼3.98, 95% CI 1.58 to 10.03) but not with the presence of a foreskin (OR¼0.67, 95% CI 0.32 to 1.40). Conclusions Infections with HPV were prevalent among sexually active heterosexual men attending the men's sexual health clinic. Associations were observed between HIV coinfection and multiple HPV infections. Further population-based studies on the prevalence of HPV genotypes are required to determine if men should be included in any future national HPV vaccination programme in South Africa.

BMC Pediatrics, Oct 15, 2018

Background: Late preterm infants, previously considered low risk, have been identified to be at r... more Background: Late preterm infants, previously considered low risk, have been identified to be at risk of developmental problems in infancy and early childhood. There is limited information on the outcome of these infants in low and middle income countries. Methods: Bayley scales of infant and toddler development, version III, were done on a group of late preterm infants in Johannesburg, South Africa. The mean composite cognitive, language and motor sub-scales were compared to those obtained from a group of typically developed control infants. Infants were considered to be "at risk" if the composite subscale score was below 85 and "disabled" if the composite subscale score was below 70. Infants identified with cerebral palsy were also reported. Results: 56 of 73 (76.7%) late preterm infants enrolled in the study had at least one Bayley assessment at a mean age of 16.5 months (95% CI 15.2-17.6). The mean birth weight was 1.9 kg (95%CI 1.8-2.0) and mean gestational age 33.0 weeks (95% CI 32.56-33.51). There was no difference in the mean cognitive subscales between late preterm infants and controls (95.4 9, 95% CI 91.2-99.5 vs 91.9.95% CI 87.7-96.0). There was similarly no difference in mean language subscales (94.5, 95% CI 91.3-97.7 vs 95.9, 95% CI 92.9-99.0) or motor subscales (96.2, 95% CI 91.8-100.7 vs 97.6, 95% CI 94.7-100.5). There were four late preterm infants who were classified as disabled, two of whom had cerebral palsy. None of the control group was disabled. Conclusions: This study demonstrates that overall developmental outcome, as assessed by the Bayley scales of infant and toddler development, was not different between late preterm infants and a group of normal controls. However, 7.1% of the late preterm infants, had evidence of developmental disability. Thus late preterm infants in low and middle income countries require long term follow up to monitor developmental outcome. In a resource limited setting, this may best be achieved by including a parental screening questionnaire, such as the Ages and Stages Questionnaire, in the routine well baby clinic visits.

South African Medical Journal, Mar 30, 2020

Intrapartum asphyxia and consequent neonatal hypoxic ischaemic encephalopathy (NHIE) is a problem... more Intrapartum asphyxia and consequent neonatal hypoxic ischaemic encephalopathy (NHIE) is a problem in low-and middle-income countries (LMICs). It has been suggested that <10% of cases of cerebral palsy (CP) in high-income countries are caused by intrapartum asphyxia. [1] However, intrapartum asphyxia may be the cause of up to 42% of CP cases in LMICs. [2] The strong relationship between CP and intrapartum asphyxia in LMICs may be due to under-resourcing and lack of access to appropriate health facilities. The incidence of NHIE varies considerably, with the greatest burden occurring in sub-Saharan Africa (14.9 per 1 000 live births) and much lower rates (1.5 per 1 000 live births) in high-income countries. [3] Results from previous studies conducted in tertiary referral centres in South Africa (SA) have demonstrated NHIE rates of 2.3-13.3 per 1 000 live births. [4-6] The rate of NHIE is likely to be considerably higher in rural areas, where there are relatively high levels of home births and health facilities are often under-resourced. Therapeutic hypothermia (TH) improves the outcomes associated with NHIE. A Cochrane review of 11 studies demonstrated that TH reduces both death and major neurodevelopmental disability. [7] Although there is some controversy regarding the safety and benefits of TH in LMICs, [8] it has been provided in the public sector in SA for several years. There is a lack of information on developmental outcomes in survivors of NHIE in SA. A retrospective review conducted in Johannesburg reported that 79.6% of survivors of NHIE were neurologically normal on follow-up, with a CP incidence of 13.2%. [4] However, no formal neurodevelopmental assessment was performed, and information about developmental outcomes was available for fewer than one-third of the neonates. Accurate information on developmental outcomes and rates of disability in survivors of NHIE is needed to enable planning of further research and to make judgements on the merits of health interventions such as TH. Objectives To compare developmental outcomes in survivors of NHIE with those in healthy children born at full term in a hospital in SA. Methods A prospective, observational study was conducted at a tertiary referral hospital in Johannesburg. Mothers of infants who had survived NHIE and had been discharged from the hospital's neonatal unit between June 2013 and December 2016 were invited to participate in the follow-up study. Those who presented at the follow-up clinic and provided consent to participate were enrolled. This open-access article is distributed under Creative Commons licence CC-BY-NC 4.0.

International Journal of General Medicine, Mar 1, 2020

Diabetes mellitus is a complex and chronic condition that requires lifelong management and intera... more Diabetes mellitus is a complex and chronic condition that requires lifelong management and interaction with a healthcare system. Failure to control risk factors through preventive care may lead to a host of diabetes-related complications. Underperforming health care systems and poor awareness among the general population/healthcare professionals has been suggested as reasons why so many patients remain undiagnosed. Due to the asymptomatic nature of early and even intermediate diabetes mellitus, several years may pass without any diagnosis before complications begin to manifest. Other factors include age, gender, ethnicity, education, marital and unemployment status which may also increase the risk of developing morbidity and mortality associated with diabetes mellitus. This review summarizes the current demographic risk factors and clinical characteristics associated with diabetes mellitus. A literature search was conducted using PubMed, MEDLINE, and Sabinet by using the following search terms: diabetes mellitus, risk factors, characteristics and complications.

Sexually Transmitted Infections, Nov 1, 2009

Sexually Transmitted Diseases, Jul 1, 2012

Background: To determine sexually transmitted infection (STI) prevalence, and patient characteris... more Background: To determine sexually transmitted infection (STI) prevalence, and patient characteristics associated with detection of urethritis/cervicitis pathogens, among HIV-infected individuals offered voluntary STI screening at a South African HIV treatment center. Methods: Individuals, asymptomatic for genital discharge, were screened for Neisseria gonorrhoeae (NG), Chlamydia trachomatis, Trichomonas vaginalis (TV), Mycoplasma genitalium (MG) infections (real-time polymerase chain reaction assay), for syphilis and herpes simplex type 2 (serologically), and for bacterial vaginosis and Candida (microscopy, women only). Patients' most recent CD4 and viral load results were recorded. Demographic, clinical, and behavioral data were collected by nurse-administered questionnaire. Results: Compared with men (n ϭ 551), women (n ϭ 558) were younger (mean age, 35.0 vs. 37.9 years; P Ͻ 0.001), reported more STIs in the past year (65.5% vs. 56.5%; P ϭ 0.002), had more urethritis/cervicitis pathogens detected (21.3% vs.16.4%, P ϭ 0.035), and were less aware of their partner's HIV status (53.1% vs. 62.3%; P ϭ 0.007). The overall prevalence of individual urethritis/ cervicitis pathogens was TV (7.6%), MG (6.1%), NG (5.4%), and C. trachomatis (2.1%). Multivariate analysis highlighted 4 significant factors associated with the detection of specific urethritis/ cervicitis pathogens, namely female gender (TV, adjusted odds ratio [aOR] 2.53, 95% confidence interval [CI]: 1.47-4.37), having a regular sexual partner in the past 3 months (NG, aOR 2.26, 95% CI: 1.01-5.08), suboptimal condom use with regular partners (TV, aOR 2.07, 95% CI: 1.25-3.42), and a history of genital warts in the past year (NG, 2.25, 95% CI: 1.26-4.03). Conclusions: Asymptomatic urethritis/cervicitis pathogens were highly prevalent in this population. Few urethritis/cervicitis pathogen-associated patient characteristics were identified, emphasizing the need for affordable STI diagnostics to screen HIV-infected patients.

InTech eBooks, Nov 9, 2016

Clinical and mortality audit is an essential part of quality improvement in health care; informat... more Clinical and mortality audit is an essential part of quality improvement in health care; information obtained in this process is used to develop targeted interventions to improve outcome. This study aimed to determine predictors of short-term survival in neonates. An existing neonatal database was reviewed. A total of 5018 neonates > 400 g admitted to a tertiary hospital (Johannesburg South Africa) between 1 January 2013 and 31 December 2015 were analysed. Mean birth weight was 2148 g (standard deviation [SD]: 972) and mean gestational age was 34.2 weeks (SD: 4.8). Overall survival was 85.6% (4294/5018). The most common causes of death were prematurity (46.2%), hypoxia (19.5%) and infection (17.2). The strongest predictors of survival were birth weight (OR 1.0; 95% confidence intervals (CI): 1.0-1.01) and gestational age (OR = 1.1, 95% CI: 1.05-1.17). Other predictors of survival included metabolic acidosis (OR = 0.14, 95% CI: 0.09-0.20), hyperglycemia (OR = 0.31, 95% CI: 0.23-0.41), mechanical ventilation (OR = 0.35, 95% CI: 0.28-0.46), major birth defect (OR = 0.12, 95% CI: 0.08-0.18), resuscitation at birth (OR = 0.39, 95% CI: 0.31-0.49) and Caesarean section (OR = 1.8, 95% CI: 1.44-2.25). In conclusion, resources need to be focused on improved care of VLBW infants.

Global Health Action, Jan 24, 2013

Background: Household contact with an index case of an infectious disease is a known risk factor ... more Background: Household contact with an index case of an infectious disease is a known risk factor for infection transmission. However, such contact may be underestimated due to the dynamic nature of households, particularly in longitudinal studies. Such studies generally begin with contact defined at a single point in time ('snap-shot'), leading to contact misclassification for some individuals who actually experienced contact before and after the snapshot. Objective: To quantify contact misclassification with index cases of disease in households. Methods: Historical data of 112,026 individuals from 17,889 households from an epidemiological study on leprosy in northern Malawi were used. Individuals were interviewed in the early 1980s and followed up over 5 years. It was possible to trace whether individuals died, changed household within the area, or moved out of the area between the two surveys. Using a 10% sample of households as the starting population and parameters for demographic and household changes over 5 years, the extent of contact misclassification was estimated through a simulation model of household dynamics, which traced contact with index cases in households over time. The model thereafter compared initial contact status and 'true' contact status generated from simulations. Results: The starting population had 11,401 individuals, 52% female, and 224 (2%) leprosy index cases. Eleven percent of the households had at least one index case resident and 10% (1, 177) of non-case individuals were initial contacts. Sensitivity of initial contact status ranged from 0.52 to 0.74 and varied by age and sex. Sensitivity was low in those aged 20Á29 and under 5 years but high in 5-to 14-year-olds. By gender, there were no differences among those aged under 5; females had lower sensitivity among those aged under 20 and higher for those above 30, respectively. Sensitivity was also low in simulations of long incubation periods. Conclusion: This work demonstrates the implications of changes in households on household contactassociated disease spread, particularly for long durations of follow-up and infections with long incubation periods where earlier unobserved contact is critical.