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Case exposure period Cases are normally interviewed about their exposures during the incubation period of their illness order cardizem once a day arteria nasi externa. Timeframe for interviews Cases and controls should be interviewed as soon as possible after their identification to minimise information bias due to inadequate or inaccurate recall of exposures during the incubation period of the illness discount 120 mg cardizem blood pressure while exercising. Protocol for control recruitment In a case control study the guiding concept in the selection of controls is that they should come from the same population at risk for the disease as the cases generic oxytrol 2.5mg otc. Requirements and issues concerning control recruitment are: delineation of an appropriate population from which controls will be recruited, either from the general population or a specific subpopulation e. Thelephone landline- based control recruitment strategies may not be valid in an era where householders have many alternatives to fixed landlines for voice communication. Making use of controls that participated in an investigation into a similar situation in the recent past may have to be considered, as well as the possibility of using cases from non-identical strains of the suspected organism as controls, that is, a case-case study design described on page 56. The control recruitment protocol should pay particular attention to non-response, that is, no answer to telephone calls or door-knocking. If non-responders are excluded purely on the basis they are unavailable on the first call, the control sample is likely to tend toward people who are regularly at home, introducing bias into the study. A standard process for managing non-responders is to make at least three attempts on different days to contact the potential control, with a minimum number of attempts in the evenings. Introductory statement for control recruitment Develop a standardised statement to read to potential controls. This statement should conform to the ethical guidelines for the preparation of information sheets, as described in the guidelines for completion of the national application form for ethical approval of research projects (available from the Health Research Council, and at the website http://www. The usual process for doing this is to ask to speak to the person in the household with the next birthday. If this person is unavailable, an arrangement should be made to call the identified individual at a more convenient time identify a process for calling at a time more convenient for the prospective control. Matching criteria Control recruitment may require matching by age, sex or geographic area of residence. Control exclusion criteria As for cases, some controls may need to be excluded from recruitment. Exclusion criteria may include: the presence of symptoms confirmed or suspected to be related to the disease of interest (i. Control exposure period The control may be questioned about exposures during the exact dates of the case’s incubation period. The advantage of this approach is that if the risk due to a particular exposure fluctuates over time (e.
Beyond this purchase cardizem line pulse pressure 45, the small increase in statistical power achieved by a further increase in the ratio does not usually justify the cost or effort required discount cardizem 180 mg with visa arteria basilar. Matching between cases and controls Matching between cases and controls helps to adjust for confounding (explained further on page 65) order wellbutrin with american express. In brief, confounding occurs when a particular factor is associated with both the exposure of interest and the outcome (disease) under investigation. For example, age would be a confounding factor in a case-control study investigating risk factors in a meningococcal disease outbreak. This is because age is closely related to the incidence of meningococcal disease (young children are more at risk than older people). If this confounding influence was not controlled, then other age-related factors (e. An appropriate technique to adjust for this confounding influence would be to make sure that each case was matched with a control of approximately the same age. Most case-control studies are matched to some extent in that they recruit controls with exposures that are matched by time period to cases. Matching on other criteria should be used sparingly and only for known, strong confounding factors for the disease under investigation. Be guided by the initial descriptive investigation and by background knowledge of the epidemiology of the illness. If the distribution of cases is strongly related to age, for instance, then matching on that basis may be appropriate. It would be rare that matching factors other than age, gender or neighbourhood would be justified in an outbreak investigation. Disadvantages to matching It can be difficult and time-consuming, and thus expensive, to find a control (or several controls) with the appropriate matching characteristics for each case. This can occur if important disease risk factors are highly correlated with the matching variables. The study will then be less able to detect the association between the risk factor and the disease. With sufficient numbers of cases and controls, it is possible to avoid matching and to control for confounding during the data analysis through the use of various statistical methods, particularly stratification and multivariate analysis. Note that the analysis of matched case-control studies differs from that of unmatched studies. If control participants have been selected on the basis of matching criteria, the analysis must account 44 for this matching, or else the estimate of the odds ratio (see below) will be biased towards 1. Matched case-control studies should be analysed either through retention of the case-control pairing (matched analysis), or by ‘breaking the match’ and accounting for the matched design through use of stratified or multivariate statistical techniques. In general, the latter option is preferable if matching 45 criteria have been limited to age and/or sex. Descriptions of these techniques are beyond the scope of this publication and a biostatistician/epidemiologist should be consulted for further guidance. Analysis of case-control study data The prevalence of characteristics or exposures among cases and controls is compared using an odds ratio, a measure of the association between exposure and illness.
Behavioral strategies often require tients with schizophrenia who are not adhering to resources and trained staff purchase cardizem 60 mg without prescription blood pressure chart urdu, yet simple reinforce- a regimen of oral agents generic 120 mg cardizem mastercard arteria axillaris. The use of a more palatable med- potential to improve adherence order seroquel line, since these agents ication than was initially prescribed has met with combine the better efficacy and tolerability of the some success in improving adherence,123,124 and atypical agents with the reliability of the depot for- the involvement of family members, schools, and mulation. Achieving full adherence mon, contributing to substantial worsening of dis- in pediatric patients requires not only the child’s ease, death, and increased health care costs. Practi- cooperation but also a devoted, persistent, and ad- tioners should always look for poor adherence and herent parent or caregiver. Adolescent patients cre- can enhance adherence by emphasizing the value ate even more challenges, given the unique develop- of a patient’s regimen, making the regimen sim- mental, psychosocial, and lifestyle issues implicit ple, and customizing the regimen to the patient’s in adolescence. Asking patients nonjudgmentally about contribute to poor adherence in children and ado- medication-taking behavior is a practical strategy lescents are similar to those affecting adults, an for identifying poor adherence. A collaborative added dimension of the situation is the involve- approach to care augments adherence. Innovative cent, with decrements in adherence occurring with methods of managing chronic diseases have had time. Most of the successful interventions in pa- personal digital assistants and pillboxes with pag- tients with chronic childhood illnesses have used ing systems may be needed to help patients who behavioral interventions or a combination of be- have the most difficulty meeting the goals of a havioral and other interventions. Blaschke reports having received consulting fees from Jazz 119-122 Pharmaceuticals, Portola Pharmaceuticals, Gilead Sciences, Aero- tem, which involves motivating adherence gen, Depomed, Kai Pharmaceuticals, and Pharsight, and reports by providing tokens or other rewards for taking having shares in Johnson & Johnson and Procter & Gamble. J Hypertens 1999;17: herence with statin therapy in elderly pa- ment: clinical applications. Medication compliance feedback persistence in use of statin therapy in elderly Clin Ther 2001;23:1296-310. Arch Intern Measurement of adherence to antiretroviral al: variability and suitability. J Clin Epidemiol event monitor: lessons for pharmacothera- Pharmacol Ther 1989;46:163-8. Improving on a antihypertensive therapy: another facet of pies: evidence for action. Geneva: World coin toss to predict patient adherence to chronotherapeutics in hypertension. Re- pact of dosage frequency on patient compli- tients to follow prescriptions for medica- sponses to a 1 month self-report on adher- ance. Cochrane Database Syst Rev 2002;2: ence to antiretroviral therapy are consistent 44. J Clin compliance with medication dosing: a liter- missions resulting from preventable adverse Epidemiol 2001;54:Suppl 1:S91-S98.