Likelihood Ratio Positive And Positive Predictive Value Health Essay Essays

Likelihood Ratio Positive And Positive Predictive Value Health Essay Essays Likelihood Ratio Positive And Positive Predictive Value Health Essay Essay Likelihood Ratio Positive And Positive Predictive Value Health Essay Essay and allows the doctor to find the importance of a positive trial consequence. An alternate method of finding the post-test chance uses likelihood ratios. The likeliness ratio ( LR ) communicates the chance that a given trial consequence would happen in a patient with the mark disease compared to a patient without the disease. Unlike PPV, LR is non reliant on pre-test chance. A positive LR is calculated by sensitivity/ ( 1 specificity ) , whereas a negative LR is calculated by ( 1 sensitiveness ) /specificity. Using a likeliness ratio nomograph, the post-test chance can be rapidly determined utilizing the deliberate LR and pre-test chance. B ) Define and contrast analytic and descriptive experimental surveies ( 2 Markss ) Descriptive surveies are used to supply information on the forms of happening of a peculiar disease within the population, such as prevalence or incidence. They describe the distribution of exposure and result variables, and are of import in exciting hypotheses such as possible hazard factors for disease. Study types include cross-sectional surveies and clinical observations described in instance studies and case-series. Analytic surveies provided critical analysis of the relationship between two factors, the consequence of an intercession or exposure on an result. Within such surveies hypotheses can be tested utilizing observation or experimentation, comparing rate of results in control group to intercession or exposed group. Such surveies include randomised controlled tests, cohort surveies and case-control surveies. Q2. An research worker would wish to measure the association of goiter and decreased I consumption in a community-based instance control survey in Nigeria. Persons with goiter will be compared with controls. The survey was located in a low income country in Nigeria and those with goiters were largely low-income persons. The research workers were surprised to happen those with a low BMI were more likely to hold goitre. They conclude that a low BMI causes goiter. a ) Do you hold or differ with the research worker? Explain your reply in a few sentences ( 2 Markss ) I disagree. The survey investigated the association of goiter with decreased iodine consumption, yet concluded that a low BMI causes goiter. Bing an experimental survey missing any intercessions, it is hard to definitively set up causality. There is no suggestion that the survey adjusted for any confounding variables related to both BMI and the development of goiter, such as income degrees or age. Failure to set for normally associated factors hinders the disclosure of true associations. For illustration, it is wholly executable that low BMI and goiter are both results of exposure to nutritionally-deficient repasts afforded by those with low income. Further survey is required to measure if low BMI meets the Bradford Hill standards for causality of goiter, using the right analytical survey type, commanding confounding and extinguishing prejudice. B ) Explain in a few words what type of bias/error may be present ( 1 grade ) Recall prejudice. Reliance on callback may take to measurement prejudice, due to inaccurate remembrance or measuring of anterior iodine consumption by both topics and controls. Further to this, choice prejudice may be if the control population was non similar plenty to the instance population. Potentially high variableness, together with measuring prejudice, threatens the internal cogency of the survey. Q3. A survey to measure the association of diabetes and smoke compared a group of hospitalised persons with diabetes ( instances ) with a group of voluntary persons without diabetes ( controls ) who were full-time employees of the same infirmary where the instances were identified. The consequences from this survey reported, for the first clip in the literature, a strong association between diabetes and smoke. a ) What type of prejudice may be present? Why do you surmise the presence of the prejudice you have identified? ( 2 Markss ) Choice prejudice. The diabetics and non-diabetics are sourced from different population samples via differing choice methods. Volunteer prejudice and built-in fluctuation between the two groups may hold unwittingly influenced the strength of association reported. B ) The magnitude of this association is likely to be either over- or underestimated. Which do you believe is the instance, and what makes you believe so? ( 1 grade ) Over-estimated. Volunteers in a survey are frequently more motivated and wellness witting than selected participants, particularly those enduring wellness complications that require hospital admittance. Furthermore, the voluntaries have regular workplace exposure to patients enduring the inauspicious effects of smoke. Therefore there is an increased likeliness of less tobacco users amongst the control group. degree Celsius ) What is the best, executable survey type you would look for to reply this type of research inquiry? ( 1 grade ) An origin cohort. This is best for analyzing the consequence of prognostic hazard factors ( such as smoking ) on an result ( diabetes ) , to clarify alterations in disease incidence, without prejudice. It is non executable to use a randomized controlled test, as it is non ethical to intentionally expose people to the wellness hazards of smoke. Q4. You have a patient who asks you if diminishing meat consumption and increasing the sum of dietetic fresh fruit and veggies will diminish their hereafter hazard of intestine malignant neoplastic disease. You search for and happen the undermentioned article a ) Write the chief survey inquiry addressed by this research paper, in your ain words. ( 1 grade ) Does ingestion of differing nutrient groups or dietetic forms alter the hazard for rectal malignant neoplastic disease in non-Hispanic White persons and African americans? B ) Convert this into the PICO format. ( 2 Markss ) Patient/Population Non-Hispanic Whites and African americans Intervention/Indicator ingestion of specific nutrient groups Comparison ingestion of specific dietetic forms Outcome altered hazard for rectal malignant neoplastic disease degree Celsius ) What is the clinical inquiry type? ( 1 grade ) Aetiology To place hazard factors in incidence of rectal malignant neoplastic disease vitamin D ) What is the survey design? ( 1 grade ) Case-control survey. vitamin E ) Identify and briefly discuss the specific characteristics of the 3 chief causes of prejudice in this survey. 100 words maximal ( 6 Markss ) The research workers acknowledge 3 chief causes of prejudice. First, utilizing the questionnaire format, they risk measurement mistake by sorting ingested nutrients into specific groups for choice, restricting weighting of peculiar nutrients in dietetic forms. Inadequate diverseness in nutrients listed contributes to this measuring prejudice. Second, trust on capable callback of nutrient ingested over the old 12 months poses a important concern for the truth of the survey, due to remember prejudice. Finally, the high Numberss of non-respondents rises inquiries about the being of differences in rectal malignant neoplastic disease hazard between participants and non-participants, implying choice prejudice. degree Fahrenheit ) The paper concludes that higher consumption of fruit, veggies and dairy were associated with reduced rectal malignant neoplastic disease in Caucasians. Discuss these consequences ( Table 2 ) in visible radiation of the 5 major points of the Bradford Hill standards for set uping causal relationships. 200 words maximal ( 10 Markss ) 1. Temporality To demo a clip relationship of alteration in rectal malignant neoplastic disease incidence over clip, the research workers requested callback of diet over the last 12 months. However, this failed to once and for all turn out that ingestion of the nutrient groups ever preceded the decrease in rectal malignant neoplastic disease incidence. 2. Consistency The survey decisions claimed to be by and large associated with similar consequences by different surveies or research workers, and referenced a few surveies back uping their decisions ( mentions 13 to 15 ) . However, this contrasted with the survey by Michels et Al, and without a far greater figure of surveies with comparable findings, consistence can non be established. 3. Strength of association Measurements for fruit, some veggies and dairy showed important decreases in the hazard of rectal malignant neoplastic disease, with odds ratios lt ; 1 back uping strong association ( statistical significance of P lt ; 0.05 ) . 4. Dose-response relationship Increasing degrees of consumption resulted in diminishing incidence for rectal malignant neoplastic disease, evidenced by diminishing odds ratios between groups Q1 to Q4. Evidence for causality requires increasing incidence of disease with increasing exposure but here an opposite relationship applies. 5. Biological plausibleness -It is plausible that nutrients rich in vitamins and fibre lessening the happening of rectal malignant neoplastic disease, as suggested by the research workers.