Epidemiology According to John Snow and William Farr - Research Paper Example

Module Epidemiology According to John Snow and William Farr Whenever epidemiology, and cholera in particular, are being discussed, two brilliant epidemiologists come to mind: John Snow, and William Farr. John Snow is regarded today as the founder of modern epidemiology, lauded for his manner of investigation of the cholera outbreak. William Farr, on the other hand, is recognized for his ingenious data collection and analysis process. While Snow is widely recognized by health professionals especially in the area of epidemiology, Farr’s work seems to have taken the unpopular route. Still both their contributions played an important part in the investigation of the cholera epidemic that terrorized the 1800’s. When the second cholera pandemic broke out and reached London in 1832, a number of theories on the causation of such catastrophic spate were proposed, including miasma or “bad air” and changes in environmental conditions (Morabia, 2001, 150th Anniversary, 2004). However, John Snow, who was a respected medical practitioner specializing in anesthesia and respiratory physiology, questioned the correctness of those theories. He observed that the symptoms were intestinal in nature, abdominal pain being one of the first complaints of the afflicted, accompanied by vomiting, diarrhea and dehydration (Eyler, 2001). At the same time, treatments that acted specific in the digestive tract seemed to alleviate early symptoms. From these observations, he proposed that cholera could not be a blood or respiratory infection but an infection of the gut. Snow proposed that the main proponent of transmission was not the soil, nor climate change or miasma as originally suggested, but the ingestion of water contaminated with fecal matter. But this did not convince the medical community. Without definitive data, Snow’s analogy was not good enough. In 1854, another wave of cholera plagued the Soho district yet again. This time, Snow suspected that an infected water pump located in Broad Street brought upon the outbreak. Following his earlier proposal that the cholera infection was from the ingestion of contaminated water and bearing a record of death from Cholera from the General Register Office, he traced the deaths attributed to cholera within the vicinity and found that they drank water from a common water pump in Broad Street. Snow elucidated this by plotting a Cholera spot map showing the areas collectively affected by the epidemic, as well as its proximity to the specific pump in question. By removing the pump handle, the incidence of cholera started to decline. At the same time, a natural experiment was brought about by a transfer of one water supply (Lambeth Company) to an area where it was believed to source out cleaner water. Snow compared the mortality rate of cholera between those who were served by the Lambeth Company, to those who were supplied contaminated water by the Southwalk and Vauxhall Company (Eyler, 2001, Brody, Russel, Vinteb-Johansen, Paneth & Rachman, 2000). Data derived from this enabled Snow to formulate the conclusion that those who were supplied with contaminated water had fourteen times higher mortality that those who were served with cleaner water (Eyler, 2001). At the same time Snow was collecting evidences to support his assumption about the causation of cholera, William Farr has been investigating the cholera epidemic as well. But while Snow’s approach was more pathological in nature, Farr geared towards the methodological process. As part of his work at the Registrar General Office, Farr has innovated a detailed disease surveillance system, “a system of standardized collection, classification, analysis and reports of causes of death” (Morabia, 2001). He wrote the “Report on the Mortality From Cholera in England 1848-1849”. In fact it was Farr’s data on the cholera cases in Broad Street that Snow used in his investigation. Farr’s cholera report outlined the relationship between different variables such as age and sex, and the incidence of cholera, the most significant findings being that the relationship between mortality and soil elevation are inversely proportional or the “law of elevation” (Short & Chetwynd, 2006). He further construed that cholera (and other diseases) was more fatal in the low places because of zymotic factors in the soil, producing polluted air that spread the disease (Eyler, 2001). In his report, Farr considered Snow’s theory to be the most plausible, maintaining however, a reservation on the logic of “waterborne” diseases. By the time of the second cholera epidemic however, Farr has become one of the strongest supporters of Snow’s “waterborne” theory. Although he still did not abandon his previous convictions of polluted air as the medium for contamination, his parametric inferences coupled with his endorsement of Snow’s theory in the report, paved way to the acceptance that cholera may be brought about by polluted water. The organism Vibrio Cholerae was isolated in 1883, ending the long debate about the epidemiology of cholera (150th Anniversary, 2004). However different the processes in which these two investigated the causation of cholera, one still cannot undermine each significant contribution to the science of epidemiology. It was Snow’s theory regarding the causation of cholera that was eventually accepted by the medical community, but it was Farr’s novel disease surveillance system that facilitated the acceptance of Snow’s theory and findings as reliable and valid. References 150 years of cholera epidemiology. (2005). Lancet, Retrieved August 4, 2009, doi:10.1016/S0140-6736(05)67345-X Brody, H., Russell Rip, M., Vinten-Johansen, P., Paneth, N., & Rachman, S. (2000). Map- making and myth-making in Broad Street: The London cholera epidemic, 1854. Lancet, 356(9223), 64. Retrieved August 5, 2009, from Academic Source Complete database. Eyler, J. M. (The changing assessments of John Snow’s and William Farr’s cholera studies. Soz Praventivmed; 46(4), 225-232. Morabia, A. (2001). Snow and Farr: A scientific duet [Editorial]. Soz Praventivmed; 46(4), 223-224. Short, H., & Chetwynd, A. (2006). Cholera—a step too Farr. Significance, 3(2), 88-90. Retrieved August 4, 2009, doi:10.1111/j.1740-9713.2006.00170.x 150th Anniversary of John Snow and the Pump Handle. (Cover story). (2004). MMWR: Morbidity & Mortality Weekly Report, Retrieved August 4, 2009, from Academic Source Complete database. Module # 2 Findley, S., Irigoyen, M., Sanchez, M., Stockwell, M., Mejia, M., Guzman, L., et al. (2008, November). Effectiveness of a community coalition for improving child vaccination rates in New York City. American Journal of Public Health, 98(11), 1959-1962. Retrieved August 5, 2009, from CINAHL with Full Text database. In 2008, Findley and her colleagues conducted a quasi-experimental, retrospective, cohort study for the purpose of re- examining the effectiveness of Start Right, a comprehensive, community-driven immunization program of outreach education and reminders that aims to improve vaccination compliance and timeliness of vaccination among a Latino, low- income community in New York City. Start Right employs the use of bilingual and other materials that are appropriate to the community it serves; education programs conducted by duly trained peer health educators; social service and outreach; as well as supported provider vaccination. This study was done retrospectively from 2006-2007. Using the National Immunization Survey methodology, four annual cohorts were derived from a total population of 10, 857 children comprising of children between the age of 19 and 35 months as of April 1. These were children born within the period of April 1999 to September 2003 at the community hospital and are all residing in a specified zip code. Distribution of cohorts are as follows: (2002) n= 2,879, (2203) n= 2788, (2004) n= 2653 and (2005) n= 2577. These four cohorts were then divided into the implementation group and the control group. The demographic data were collected using the community hospital’s database, and the immunization records were obtained from the New York Citywide Immunization registry or the CIR. CIR records were available for 88% of the total population, 93.9% (n= 9511) belonged to the Start Right or implementation group, and 87.0% belonged to the control group. To measure the effectiveness of the Start Right program, the researchers collected data regarding timeliness of immunizations for the 4 diphtheria-tetanus-pertussis (DTaP); 3 doses of Polio; 1 dose of measles-mumps-rubella (MMR); 3 doses of Haemophillus Influenza b; and 3 doses of Hepatitis B or what is most commonly known as the 4:3:1:3:3 series. The researches also looked at the timeliness of the last DTaP dose or the DTaP4 by computing for how many days have elapsed between the date that the immunization became overdue, and the actual date that the last dose of DTaP was administered. The data collected were then analyzed with the Stata 9.0. using the X2 and the unpaired 2-sample Student’s t test for testing the significance of difference between the coverage and the timeliness of immunization. The adjusted odd ratios for the intervention effect on the immunization status were then computed using logistic regression, making sure to control for the Latino ethnicity and Medicaid enrollment. Among the sample, 8.2% were enrolled in Start Right. Children in the Start Right and the control group were similar in their mean age (27.4 months). However, children in the Start Right group tend to be enrolled in Medicaid (85.1%) when compared with the control group (78%). At the same time, the Start Right group had more Latinos than the control group (92% vs 85.1%). Immunization coverage turned out to be much higher in the Start Right group (11%), when compared to the control group (X2 = 44.6%; P < .001). The Start Right group also completed the immunization series ahead by 11 days. When the ethnicity is controlled, the Smart Right group was more likely to have up-to-date immunization than those in the control group, on the other hand, Latino ethnicity and Medicaid enrollment had any significant effect in the immunization coverage. This study has illustrated that the Smart Right program was instrumental in the improvement of compliance and timeliness of vaccination among children in a Latino, low-income community of New York City. The use of community driven-program relied on parent empowerment employing methods such as one-on-one teaching and handouts; and constant reminders through telephone calls and home visits among others. This enhanced community ownership of the programs proved to be effective in educating parents as to the importance of childhood vaccination as well as the timeliness of such. Because this research utilized purposive sampling as the sample selection process, and because control for the ethnicity and Medicaid membership were employed, the results of this study is deemed generizable to the population served or will be served by the immunization programs using strategies similar to the Start Right. However, the use of CIR records for tracking of immunization compliance resulted in 24% dropout rate due to incomplete provider reporting, thus presenting a threat to internal validity. Future researchers may benefit from using a comprehensive immunization record system or including immunization cards from the parents, in order to ensure the completeness of information. An alternative research design for this particular study would be the experimental research design utilizing random assignment for the implementation group and the control group from the total population of 10, 857 children. Random assignment, along with the manipulation of independent variable, which is the Start Right program, and the employment of a control group would ensure that the question of effectiveness of the community coalition would still be answered, at the same time, controlling or eliminating all possible sources of variation. Module # 3 Baum, C., Connor, L., Morrison, T., Hahn, M., Dromerick, A., & Edwards, D. (2008). Reliability, validity, and clinical utility of the Executive Function Performance Test: a measure of executive function in a sample of people with stroke. American Journal of Occupational Therapy, 62(4), 446-455. Retrieved August 5, 2009, from CINAHL with Full Text database. Rationale of the Study The purpose of this study was to examine the reliability and validity of the Executive Function Performance Test or EFPT in the mild and moderate stroke population. Specifically, it aimed to 1) determine the EFPT’s interrater reliability and internal consistency, 2) determine EFPT’s validity in the mild stroke, moderate stroke and healthy sample, and 3) evaluate its concurrent validity by comparing results on EFPT to results on neuropsychological tests. The researchers proposed three hypotheses. These are 1) that healthy control participants would perform significantly better on the EFPT that people with stroke, 2) that participants with mild stroke would perform significantly better that those with moderate stroke, and 3) that the EFPT score would show significantly moderate correlations with neuropsychological assessments of executive function. Study Design This study utilized a comparative design. The researchers compared the results of EFPT across the three groups: 73 participants who have suffered from stroke 6 months prior; living in the community; and not enrolled in a rehabilitation program were recruited for the implementation group were divided into the mild stroke and moderate stroke group; and 22 healthy participants that matched the age and education of those in the implementation group were assigned to the control group. The results of the EFPT were then compared to results from other measures of cognitive function to test for the validity. Variables of the Study The demographic variables included in the study include age, race, and education. The independent variable is the presence and severity of stroke. The dependent variables in this study are the scores of the EFPT, the Neuropsychological Tests, the Short Blessed Test and the Function Outcome Measures. The Executive Function Performance Test The EFPT was developed to provide a standardized assessment of cognitive function. In contrast with current performance evaluation tools used to examine cognitive function, the EFPT does not measure what people cannot do. Instead, it measures what they can actually do, and what specific assistance is needed in order for them to successfully perform the tasks. The EFPT uses tasks such as cooking, using the telephone, managing medications and paying bills to measure five specific executive function components. The executive function components that EFPT measures are: 1) the initiation of a task, 2) organization, 3) sequencing, 4) safety and judgment and 5) completion. Initiation of a task involves the ability of a person to start or commence the task. Organization involves the correct retrieval and arrangement of the tools necessary to perform the task. EFPT measures sequencing through observation of the execution of the steps or the performance of the task in correct order. On the other hand, safety and judgment entails the avoidance and prevention of dangerous situations. The last component completion is measured through the person’s actions to indicate awareness that the task is finished. The EFPT also makes use of a cuing system that facilitates identification of the necessary assistance necessary for the successful performance of each task. Five levels of cuing can be given to a person. First is “0” or when a person performs the task components without any cue required. The next level is “1” verbal guidance, or when a person needs verbal cues. Level 2 is gestural guidance or when a person requires cues that are gestural in nature. In level 3 or direct verbal assistance, a person needs a direct verbal cue to action. Level 4 is physical assistance or when a person needs physical help, and the last level, “5”, is when the facilitator of the test has to perform the task for a person. The highest level of cuing necessary is recorded across all the task components performed and scored on a scale of 0 to 5. Scores were then computed according to the executive function component (ranging from 0 to 20), the task score is computed by adding the total scores for each task (ranging from 0 to 25), and the total score of all the fours tasks (ranging from 10-100). Operational Definition Mild and moderate stroke classification was operationalized using the National Institute of Health Stroke Scale (NIHSS). The NIHSS is a 13-item test that measures cognitive, sensory and motor impairments among those who suffered from stroke. A score of 5 or less placed the participants in the mild stroke category, while a score of 6-15 on the NIHSS indicated moderate stroke. Performance of executive tasks was operationalized using the EFPT. Executive function is measured though the performance of the four tasks. The cooking task called for the participants to cook oatmeal following specific instructions. The telephone task included looking up the telephone number of a grocery store, calling it and inquiring about deliveries. Managing medications asked the participants to select the correct medicine (a placebo) from the choices given and take it with food as instructed. Paying the bills was observed through the ability of the person to sort through the bills, pay them and balance the account. Cognitive functions were further operationaized through the Short Blessed Test for memory, orientation and concentration; the Neuropsychological Tests including Animal Naming, Trailmaking Test and the Wechsler Memory Scale- Revised; and the Functional Outcome Measures FIM and FAM. Reliability Reliability of an instrument is its ability to test something consistently, or it yields similar results every time it is used. Interrater reliability is the ability of the same instrument to yield similar results even when different assessors administer it, that is, three trained raters administered EFPT simultaneously to 10 participants. Intenal consistency, or the degree to which the EFPT measures executive functions was tested using the Chronbach’s alpha. Validity Validity is the ability of an instrument to measure what it’s supposed to measure. For this study, the construct validity and the concurrent validity are measured. Criterion validity, or the ability of EFPT to discriminate a trait, was measured using the one-way ANOVA comparing differences in performance among the 3 groups. Concurrent validity is the accuracy of EFPT in measuring cognitive function. This was established through the comparison of EFPT results among the stroke group with the results of the Short Blessed Scale, the Neuropsychological Tests and the Function Outcome Measures. Table 1: Demographic Characteristics and Performance on the EFPT by group Table 1 presents the demographic characteristics of the study participants and their performance in the EFPT. Among the 95 participants, 59 had mild stroke while 14 had moderate stroke, while the control group had 22 participants. The control participants were slightly younger than those in the stroke group. They were predominantly female (n=71), and white (n=63). Table 1 also shows that the control group had more years of education. The EPT total score, EPT task scores and EF component scores were consistently higher in the moderate stroke and lowest among the control group. Strengths and limitations The strength of this study lies in the clarity and completeness of the report. Another strength is in the matching of the age and years of education characteristics of the sample. Limitations of this study are the small number of participants, and the purposive sampling technique. A replication of this study using a larger sample size and random sampling will establish the reliability and validity of the EFPT further. Module #4 Haukoos, J., Witt, M., Coil, C., & Lewis, R. (2005). The effect of financial incentives on adherence with outpatient human immunodeficiency virus testing referrals from the Emergency Department. Academic Emergency Medicine, 12(7), 617-621. Retrieved August 5, 2009, from CINAHL with Full Text database. Purpose of the Study This study by Haukoos and her colleagues examined if a $25 financial incentive had improved adherence of patients referred by the emergency department (ED) for attending HIV counseling and HIV testing. Study Protocol The participants in the intervention group were offered a $25 incentive provided that they complete the pre-test counseling, HIV testing, and post-test counseling. Verbal and written instructions were given to the patients, including reminders of the $25 incentive that was due them. Those who completed the HIV counseling and testing were awarded their $25 financial incentive. Sampling and Inclusion Criteria Making use of convenience sampling, a total of 372 patients who presented to the ED between January 10, 2002 and September 1, 2003 were included in this study. Inclusion criteria are referral of the ED to HIV counseling and testing resulting from identification of risk factors, history suggestive of immunodeficiency, physician suspicion for HIV, laboratory results suggestive of HIV, physical examination findings suggestive of HIV, history suggestive of HIV, emergency department diagnosis suggestive of HIV, and patient’s personal request for testing. Research Design This study utilized a quasi-experimental research design. It is considered quasi-experimental because it employed two of the three critical characteristics of an experimental design, which are manipulation of the independent variable, and the use of a control group. Data were collected in three different phases utilizing different samples for each. The participants in the first and third phases were the control group while those in the second phase was the intervention group. Manipulation of the independent variable was in the use of no incentive during the first and third phases and the use of a $25 incentive for the second phase. This study, however, used convenience sampling, which detracts from being a true experimental design. Randomization True experimental designs make use of randomization in order to control for possible biases brought about by human factors that can significantly affect the reliability and validity of the study results. Randomization gives the participants fair and equal chance to both be in the intervention or the control group, thus creating groups that are comparable in their characteristics, and controlling for extraneous and confounding variables. Randomization is achieved through the use of a table of random numbers usually included in most research books, or by use of a computer program. Results and Conclusion The mean age of the participants was 32 years old, 66% of which are males and 34% were females. Majority of the patients referred to the HIV testing and counseling were Hispanic, accounting for 40%, followed by African American (32%). There was a significant difference in the race and ethnicity between the control group and the intervention group (p- 0.006). 23% of those who received the financial incentive completed the HIV counseling and testing, while only 8% of those who did not get financial incentive completed. Of those who completed the HIV counseling and testing, none was found to be HIV positive. The researchers considered incidental data derived from this study because data showed that African Americans and Hispanics have a poor chance of following through with the testing. The authors felt that the increase in the compliance to HIV counseling and testing was modest and the fact that none of those who completed the counseling and testing were found to be HIV positive. This means that those who are really at risk for HIV still refuse to be tested and counseled, even when there is financial incentive involved. Because of this, the researchers suggested point-of-care testing in order to ensure that a significant number of patients in the race and ethnicity that showed poor compliance will be tested for HIV. Strengths and Weaknesses The strength of this study is the recognition of the researchers of their limitations and the possible biases that may have affected the validity of the results of this study. The use of convenience sampling opens the possibility of referral bias resulting from the characteristics of the physician clustered through the three phases. Since criteria for referral relied specially upon the physician assessment (save for laboratory findings and patient’s personal request), there might be a threat of selection effect in that the rate for referral may be affected by the physicians’ individual characteristics. Another bias that resulted from the use of convenient sampling was the significant difference between the two groups in terms of race and ethnicity, which the researchers controlled with the use of multivariate logistic regression. The researchers utilized control groups in an effort to control the lack of randomization and to control for referral bias. However, the sample size was fairly small, presenting a question in whether the results are true of the intervention or just results of chance. The researchers also reported stringent monitoring of data, as well as interpretation and generalization. Module #5 Coleman, V., Morgan, M., Carlson, R., Hawks, D., & Schulkin, J. (2009). Patient Perceptions of Obstetrician-gynecologists Practices Related to HIV Testing. Maternal & Child Health Journal, 13(3), 355-363. Retrieved August 6, 2009, from CINAHL Plus with Full Text database. Objectives and Hypothesis This study conducted by Coleman et. al. examined the rates of HIV testing among the obstetrician-gynecologists’ patients, both pregnant and non-pregnant; how these patients perceive HIV testing and their own risk for HIV; ascertain why they refuse to be tested; and their recollection of how their obstetrician-gynecologists discussed HIV testing with them. The researchers hypothesized that pregnant women, women who are getting preconception care, and those who were at high risk for HIV, would remember being referred for HIV testing by their obstetrician-gynecologists. Goal and Recommendation The researchers carried out this research for reason that obstetrician-gynecologists are the primary providers of care to a population that is fast becoming a cause for concern because of their rapid growth rate for diagnosis of HIV. Thus, they are at the very core of the HIV testing recommendation recently published by the Centers for Disease Control and Prevention (CDC), which is routine testing for adolescents and adults. It is imperative that obstetrician-gynecologists take on this role to heart and be vigilant in recommending HIV testing to their patients. Research design The researchers used descriptive comparative design for the purpose of determining the sample’s perception of their obstetrician-gynecologists’ practice regarding recommendation for HIV testing. Responses of patients were compared in terms of Age, race, income, education, marital status, pregnancy status, provider identity, and insurance status. A parallel survey was also conducted to compare the obstetrician-gynecologists’ reported practice of HIV testing and the patients’ recollection of their obstetrician-gynecologists recommending HIV testing to them. Continuous Variables Continuous variables are variables that are capable of taking an infinite number of values between two points and are not restricted to whole numbers. The continuous variables used in this study are age and family income. These are considered continuous variables because the answers can range from zero to infinity. Statistical Procedures Analysis of data was facilitated with the use of SPSS 14.0. The independent samples t-test was used to analyze data derived from continuous measures. The independent samples t-test is a statistical analysis intended to compare data between two groups on a given variable or bivariate analysis. For categorical variables on the other hand, the chi square test was utilized to analyze categorical data. The chi-square is useful in comparing differences in data between two or more groups. This is considered multivariate analysis of data. Results from these analyses were further subjected to either the linear regression analysis or principal components analysis (PCA) to delineate specific factors that facilitated patients’ recall if their obstetrician-gynecologist recommended HIV testing to them. Linear regression attempts to depict the relationship between two variables (bivariate) while PCA is a multivariate analysis used to deconstruct the numerous variables into principal components, identifying if there are other factors that may have contributed to the patients’ decision to be tested or not. Bias The most evident bias in this study is the measurement bias. As the researchers reported, patients’ responses may have been influenced by the fact that this is a sensitive issue and the manner of fact that the obstetrician-gynecologists’ were used to distribute and collect the patient survey forms, the patients may have felt to model their responses according what they think is acceptable or expected response. At the same time, some items were found to be ambiguous possibly affecting the way the patients responded to said questions. This affects the results greatly in that, patients may have answered otherwise if the question was stated in a way that was more understandable and avoids bias brought about by differences in interpretation. Table 4 A part of this study is the parallel physician study where the responses of the patients were compared to their obstetrician-gynecologists’ responses. Table 4 illustrates that physicians have strongly or moderately recommended HIV testing for patients who have reported multiple sexual partners. However, less than 50% of the patients do not recall being asked about this by their obstetrician-gynecologists (52% for non-pregnant and 39% for pregnant). It was also evident that obstetrician-gynecologists report to recommending HIV testing to all pregnant patients. This contradicts data collected from the patients. Only 22% of non-pregnant patients and 39% of patients remembered being recommended for HIV testing by their obstetrician-gynecologists. Results Chi-square analysis revealed that Hispanic and African-American patients were more likely to recall being recommended for HIV testing by their obstetrician-gynecologists. Using a degree of freedom (3), chi-square value of 17.3 and using the predetermined alpha level of 0.05, the probability level of P < 0.01 is determined which is higher than the accepted significance level of 0.05. Therefore it shows there is a significant relationship between race and recollection of the patients being recommended for HIV testing by their obstetrician-gynecologists. Limitations One of the limitations of this study is the fact that the researchers had little control over the distribution and collection of survey forms. The survey forms were distributed to the patients and collected by the providers which may have affected the sample distribution and characteristics resulting to a sample that may not be representative of the population, thus, affecting the generalizability of the results. 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