Measuring additive interaction using odds ratios

Interaction measured on the additive scale has been argued to be better correlated with biologic interaction than when measured on the multiplicative scale. Measures of interaction on the additive scale have been developed using risk ratios. However, in studies that use odds ratios as the sole measure of effect, the calculation of these measures of additive interaction is usually performed by directly substituting odds ratios for risk ratios. Yet assessing additive interaction based on replacing risk ratios by odds ratios in formulas that were derived using the former may be erroneous. In this paper, we evaluate the extent to which three measures of additive interaction – the interaction contrast ratio (ICR), the attributable proportion due to interaction (AP), and the synergy index (S), estimated using odds ratios versus using risk ratios differ as the incidence of the outcome of interest increases in the source population and/or as the magnitude of interaction increases. Our analysis shows that the difference between the two depends on the measure of interaction used, the type of interaction present, and the baseline incidence of the outcome. Substituting odds ratios for risk ratios, when calculating measures of additive interaction, may result in misleading conclusions. Of the three measures, AP appears to be the most robust to this direct substitution. Formulas that use stratum specific odds and odds ratios to accurately calculate measures of additive interaction are presented

Cervical Precancerous Lesions in HIV-Positive Women in Cameroon: Prevalence, Predictors and Potential Impact of Screening

Cervical cancer is the most common cancer in women in low-income countries. Although cervical cancer incidence and mortality is higher in HIV-positive women, resource limitations restrict the implementation of systematic screening programs in these women. The purpose of this dissertation was to explore the potential for targeted screening by assessing the prevalence and clinical predictors of cervical squamous intra-epithelial lesions (SIL) in HIV-positive women in Cameroon. Furthermore, we sought to explore the potential impact of antiretroviral therapy and screening on mortality from cervical cancer. We initially conducted a cross-sectional study of HIV-positive women in Cameroon. A total of 282 women, aged 19 to 68 years with a median CD4 cell count of 179 cells/microliter, were enrolled. SIL were detected in 43.5% of the 276 women with satisfactory samples: including high-grade SIL (HSIL) in 3.3%. None of the clinical factors assessed significantly predicted the presence of any lesion. Among patients with CD4 counts less than 200 cells/microliter, the prevalence of SIL was higher in patients aged 26-59 years compared to younger women, while there was essentially no difference amongst women with CD4 counts greater than 200 cells/microliter. Using a Markov state-transition model of a cohort of HIV-positive women in Cameroon, we examined the potential impact of scenarios including: no HAART and no screening (NHNS); HAART and no screening (HNS); and HAART and screening once at age 35 (HS35). Compared to NHNS, lifetime cumulative cervical cancer mortality doubled with HNS. It will require 202 women being screened at age 35 to prevent one cervical cancer death amongst women on HAART. The high prevalence of SIL in women initiating antiretroviral therapy in Cameroon underscores the need for screening in this population. With neither age nor any other clinical factor being a good predictor of SIL, alternative affordable screening options need to be explored. Furthermore, the long-term evolution of SIL needs to be assessed in prospective studies of these women. Screening has the potential of reducing cervical cancer mortality in HIV-positive women in Africa. The cost of achieving such an effect needs to be assessed

Delayed diagnosis of lymph node tuberculosis: time-honored importance of a thorough clinical examination, Cameroon

History taking and physical examination is the cornerstone of medical diagnosis as will lead to correct diagnosis 90% of the time. We report a case of a 30-year-old black African man with lymph node tuberculosis diagnosed one year and six months later after onset of symptoms and signs. Clinicians especially those in resource-limited settings should go in for thorough history taking and complete physical examination which is the basis for correct clinical diagnosis, will provide valuable guide in deciding which tests to order and thus laboratory tests done for confirmatory purposes and also, has a cost-effective benefit for the patient.Keywords: History taking, physical examination, lymph node, diagnosis, resource-limited setting

Nurses and challenges faced as clinical educators: a survey of a group of nurses in Cameroon

BACKGROUND: Clinical teaching is an important component of clinical education. In nursing, clinical teaching is ensured by clinical nurse educators (CNEs). This study aimed at describing the major challenges faced by CNEs in Cameroon. METHODS: In a qualitative study, supplemented with quantitative methods, CNEs were enrolled from three health districts to represent their frequency in Cameroon’s health delivery system. RESULTS: A total of 56 CNEs participated in the study, of whom, as many as 58.9% acknowledged always facing challenges in clinical teaching and supervision. The major challenges identified were the lack of opportunities to update knowledge and skills, students’ lack of preparedness and the CNEs not being prepared for clinical teaching. CNEs attributed these challenges in major part to the lack of incentives and poor health policies. CONCLUSION: CNEs in Cameroon do indeed face major challenges which are of diverse origins and could adversely affect teaching in clinical setting

Efficacy and clinical effectiveness of influenza vaccines in HIV-infected individuals: a meta-analysis

Abstract Background Though influenza vaccines are the cornerstone of medical interventions aimed at protecting individuals against epidemic influenza, their effectiveness in HIV infected individuals is not certain. With the recent detection of influenza strains in countries with high HIV prevalence rates, we aimed at evaluating the current evidence on the efficacy and clinical effectiveness of influenza vaccines in HIV-infected individuals. Methods We used electronic databases to identify studies assessing efficacy or effectiveness of influenza vaccines in HIV patients. We included studies that compared the incidence of culture- or serologically-confirmed influenza or clinical influenza-like illness in vaccinated to unvaccinated HIV infected individuals. Characteristics of study participants were independently abstracted and the risk difference (RD), the number needed to vaccinate to prevent one case of influenza (NNV) and the vaccine effectiveness (VE) computed. Results We identified six studies that assessed the incidence of influenza in vaccinated HIV-infected subjects. Four of these studies compared the incidence in vaccinated versus unvaccinated subjects. These involved a total of 646 HIV-infected subjects. In all the 4 studies, the incidence of influenza was lower in the vaccinated compared to unvaccinated subjects with RD ranging from -0.48 (95% CI: -0.63, -0.34) to -0.15 (95% CI: -0.25, 0.05); between 3 and 7 people would need to be vaccinated to prevent one case of influenza. Vaccine effectiveness ranged from 27% to 78%. A random effects model was used to obtain a summary RD of -0.27 (95%CI: -0.42, -0.11). There was no evidence of publication bias. Conclusion Current evidence, though limited, suggests that influenza vaccines are moderately effective in reducing the incidence of influenza in HIV-infected individuals. With the threat of a global influenza pandemic, there is an urgent need to evaluate the effectiveness of influenza vaccines in trials with a larger number of representative HIV-infected persons

High birth weight in a suburban hospital in Cameroon:An analysis of the clinical cut-off, prevalence, predictors and adverse outcomes

BACKGROUND AND AIMS: High birth weight (HBW) increases the risk of maternal and fetal morbidity and mortality. Its prevalence and adverse outcomes may be reduced if risk factors are identified and managed during pregnancy. The cut-off value for HBW remains debatable. The objectives of this study were to identify the optimal cut-off value and determine the prevalence, predictors and adverse outcomes of HBW in a suburban area of Cameroon. DESIGN: A 6-year retrospective register analysis and a 3-month prospective phase. SETTING: A secondary care level (regional) hospital in the city of Buea (southwest region of Cameroon). PARTICIPANTS: Women who delivered in this hospital over a 6-year period (retrospective phase) and consenting pregnant mothers and their infants (singletons, born at >28 weeks gestation) (prospective phase). OUTCOME MEASURES: 90th centile of birth weights; prevalence of HBW defined as birth weight above the 90th centile; sociodemographic, maternal and obstetrical factors associated with HBW; maternal and neonatal adverse outcomes of HBW. RESULTS: Of the 4941 newborns reviewed in registers, the 90th centile of birth weights was 3850 g. Using this new cut-off, we obtained a prevalence of 14.0% for HBW in the 200 newborns included in the prospective phase. This was significantly higher than the prevalence (9.5%) yielded when the traditional cut-off of 4000 g was used (p=0.003). None of the factors assessed was independently associated with HBW. Newborns with HBW were more likely to have shoulder dystocia (p<0.01), and their mothers more likely to suffer from prolonged labour (p=0.01) and postpartum haemorrhage (p<0.01). CONCLUSIONS: The results of this study suggest that the cut-off for HBW in this population should be 3850 g. Thus, 3 of every 10 babies born with HBW in this hospital are likely not receiving optimal postnatal care because 4000 g is currently used to qualify for additional support

Hypertension, an Emerging Problem in Rural Cameroon: Prevalence, Risk Factors, and Control

Background. Despite the increasing trends suggesting that hypertension is a growing public health problem in developing countries, studies on its prevalence, associated risk factors, and extent of blood pressure control have been inequitably done in urban and rural communities in these countries. We therefore aimed to determine the prevalence of hypertension and extent of blood pressure control in rural Cameroon. Methods. This was a community-based cross-sectional study conducted in rural Cameroon (the Moliwe Health Area). Participants aged 21 years and above were recruited by a probability proportional to size multistage sampling method, using systematic sampling for household selection and random sampling for participant selection. Blood pressure, weight, and height were measured by standard methods. Hypertension was defined as BP ≥ 140/90 mmHg. Results. The prevalence of hypertension among the 733 participants recruited was 31.1% (95% CI: 27.8–34.6) and 71% (95% CI: 58.7–81.7) of these hypertensive patients were newly diagnosed. Only 21.2% (95% CI: 12.1–33.3) of known hypertensives had a well controlled BP. Age, obesity, low educational status, and being married were associated with HTN after adjusting for confounders. Conclusions. The high prevalence of hypertension and inadequate BP control among known hypertensives in rural Cameroon warrants greater sensitization and regular screening to reduce hypertension-related morbidity and mortality

Knowledge, attitudes and practices regarding depression among primary health care providers in Fako division, Cameroon

Abstract Background Mental health and mental illness are often overlooked in the management of patients in our health services. Depression is a common mental disorder worldwide. Recognising and managing mental illnesses such as depression by primary health care providers (PHCPs) is crucial. This study describes the knowledge, attitudes and practices (KAP) of PHCPs regarding depression in Fako Division. Methods A cross-sectional study was conducted among PHCPs (general practitioners, nurses, pharmacy attendants and social workers) in public-owned health facilities in the four health districts in Fako Division. Participants were selected by a consecutive convenience sampling. A structured questionnaire including the Depression Attitude Questionnaire (DAQ) was used to collect information about their socio-demographic characteristics, professional qualifications and KAP about depression. Results The survey had a response rate of 56.7%. Most of the 226 participants (92.9%) were aware that depression needs medical intervention. Only 1.8% knew a standard tool used to diagnose depression. Two-thirds agreed that majority of the cases of depression encountered originate from recent misfortune. About 66% felt uncomfortable working with depressed patients. Also, 45.1% of PHCPs did not know if psychotropic drugs were available at pharmacies within their health area. Very few (15.2%) reported to have prescribed psychotropic drugs. Less than half (49.1%) of the participants had prior formal training in mental health. Conclusion PHCPs in Fako Division tend to have limited knowledge and poor attitudes regarding depression. Practices towards diagnosis and management of depression tend to be inadequate. There is an urgent need to train PHCPs in mental health in general and depression diagnosis and management in particular

Potential impact of infant feeding recommendations on mortality and HIV-infection in children born to HIV-infected mothers in Africa: a simulation

Abstract Background Although breast-feeding accounts for 15–20% of mother-to-child transmission (MTCT) of HIV, it is not prohibited in some developing countries because of the higher mortality associated with not breast-feeding. We assessed the potential impact, on HIV infection and infant mortality, of a recommendation for shorter durations of exclusive breast-feeding (EBF) and poor compliance to these recommendations. Methods We developed a deterministic mathematical model using primarily parameters from published studies conducted in Uganda or Kenya and took into account non-compliance resulting in mixed-feeding practices. Outcomes included the number of children HIV-infected and/or dead (cumulative mortality) at 2 years following each of 6 scenarios of infant-feeding recommendations in children born to HIV-infected women: Exclusive replacement-feeding (ERF) with 100% compliance, EBF for 6 months with 100% compliance, EBF for 4 months with 100% compliance, ERF with 70% compliance, EBF for 6 months with 85% compliance, EBF for 4 months with 85% compliance Results In the base model, reducing the duration of EBF from 6 to 4 months reduced HIV infection by 11.8% while increasing mortality by 0.4%. Mixed-feeding in 15% of the infants increased HIV infection and mortality respectively by 2.1% and 0.5% when EBF for 6 months was recommended; and by 1.7% and 0.3% when EBF for 4 months was recommended. In sensitivity analysis, recommending EBF resulted in the least cumulative mortality when the a) mortality in replacement-fed infants was greater than 50 per 1000 person-years, b) rate of infection in exclusively breast-fed infants was less than 2 per 1000 breast-fed infants per week, c) rate of progression from HIV to AIDS was less than 15 per 1000 infected infants per week, or d) mortality due to HIV/AIDS was less than 200 per 1000 infants with HIV/AIDS per year. Conclusion Recommending shorter durations of breast-feeding in infants born to HIV-infected women in these settings may substantially reduce infant HIV infection but not mortality. When EBF for shorter durations is recommended, lower mortality could be achieved by a simultaneous reduction in the rate of progression from HIV to AIDS and or HIV/AIDS mortality, achievable by the use of HAART in infants

Knowledge and perceptions towards malaria prevention among vulnerable groups in the Buea Health District, Cameroon

BACKGROUND: Malaria is a public health problem especially in vulnerable groups such as pregnant women and children under five years in Cameroon including the Buea Health District (BHD). Misconceptions concerning it exist. This study assessed the level of knowledge and perceptions towards malaria control among pregnant women and mothers/caretakers of under-fives in the BHD. METHODS: A community-based cross-sectional study was conducted in the BHD in August, 2011 in five health areas. A questionnaire was used to collect data on demographic variables, knowledge and perceptions towards malaria control from 443 respondents aged 15–73 years. RESULTS: Of the 443 respondents interviewed, 99% had heard about malaria. Awareness of malaria was similar in rural (98.04%) and urban (98.97%) areas. The health facility was the most popular source of information (74%). The radio, television, tracts/posters and the community relay agents (CRAs) all informed significantly higher proportions of respondents in the urban than rural communities (P <0.05). Overall, 92% of respondents had the right perception of malaria and 88% knew at least one correct sign/symptom of malaria. The most recognised sign of malaria was fever. When all aspects of malaria were considered, majority (88%) of respondents had good levels of knowledge on malaria. The level of good knowledge in respondents with ≥ secondary school education (91%) was significantly higher (P = 0.01) than in those with ≤ primary school level (83%). Overall, 99% had heard about insecticide treated nets (ITNs); 99% perceived ITNs as a good means to prevent malaria; most respondents (57%) used ITNs mainly for protection against mosquito bites while 48% used them for protection against malaria. CONCLUSION: Respondents with no formal education had a poor level of knowledge on malaria. Hence, new strategies for sensitization messages involving their active participation need to be developed