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DATA COLLECTION

DATA COLLECTION. Dr. Vladimir Ba cârea. MEDICAL DATA COLLECTION. Defining medical data Means of medical data collection Methods of medical data collection Research instruments Data analysis plan. VARIABLES. Medical data = variables

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DATA COLLECTION

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  1. DATA COLLECTION Dr. Vladimir Bacârea

  2. MEDICAL DATA COLLECTION Defining medical data Means of medical data collection Methods of medical data collection Research instruments Data analysis plan

  3. VARIABLES Medical data = variables A variable = function (it can take different values for each sample or target population element) Establishing variable type

  4. VARIABLES TYPES Variables are classified in two groups: Quantitative variables (which can be measured) Qualitative variables (which can’t be measured)

  5. VARIABLES TYPES Qualitative variables are: Nominal variables = groups of elements which can’t be organized (hair color) Ordered nominal variables = the conclusions can be grouped e.g.: the treatment efficiency: very good/good/bad Binary variables = there are only two possibilities: ill/healthy, YES/NO

  6. VARIABLES TYPES Quantitative variables are: • Continuous variables = measurable variables which can take an infinite number of values, usually placed in an interval e.g.: values of cholesterol, values of blood pressure • Discontinuous variables = variables which can only take integer values e.g.: APGAR score

  7. VARIABLES TYPES Survival variables • It corresponds to the time passed between a subject inclusion in a study and a predefine element turn up (death, metastasis, complication)

  8. MEAN OF DATA COLLECTION Regarding studied elements: • Exhaustive collection. All population subjects that we desire to study. Hard to accomplish due to high costs or study population alteration. • By sampling. Is the method used in medical studies.

  9. MEAN OF DATA COLLECTION Regarding the length of collection: • Transverse. A group is studied in a precise moment in time. • Longitudinal (extended in time): • Retrospective – based on medical registers • Prospective – data collected on pre-established time intervals.

  10. METHODSOF MEDICAL DATA COLLECTION • The interview • Individual interview • Group interview • It involves similar methodological steps with the observation

  11. METHODSOF MEDICAL DATA COLLECTION • The questionnaire • Introduction • Body • Questions statement • Questionnaire graphics

  12. METHODSOF MEDICAL DATA COLLECTION • Existing records • Hospital observation papers • Consultation records • Laboratory records • Operating room records

  13. Research instruments • Choosing the research instrument depends on: • Study objective • The researched disease • The population to study

  14. Research instruments • Library study • The computer • Experimental determinations • Statistics • Human mind • Language and communication facilities

  15. Research instruments • Library study • Library catalogs • Indexes and abstracts • Librarian references • The search through library book shelves

  16. Research instruments • The computer • The Internet and World Wide Web (WWW) • Medical data search and selection engines • Electronic mail (e-mail)

  17. Research instruments • Experimental determinations • Qualitative and quantitative phenomenon quatification • Variables standardization (nominals ordinals, etc.) • Method validation • Method reproducibility

  18. Research instruments • Statistics • Descriptive statistics • Inferential statistics • Statistical tests – statistical significance

  19. Research instruments • Human mind • Statistically significant • vs. • Scientific significant

  20. Research instruments • Language and communication • Stating facts • Oral • In writing • Verbal nuance

  21. Data analysis plan • Defining the purpose • Defining the objectives • Defining the working hypotheses • Sampling • Ensuring data quality • Testing the hypotheses

  22. Data analysis plan • Defining the purpose: • To describe a health issue (to evaluate the pulmonary tuberculosis in Mures county) • To evaluate a diagnostic procedure (to establish the quality of ultrasonography in diagnosing gallstones)

  23. Data analysis plan • Defining the purpose: • To evaluate a therapeutic approach (to demonstrate the efficiency of laparoscopic cholecystectomy for gallstones) • Risk and/or prognosis factor research (to demonstrate the role of heptavalent chromium in the etiology of chronic obstructive pulmonary disease)

  24. Data analysis plan • Defining the study objectives: • To describe a health issue • Main objective (to calculate the prevalence of pulmonary TB in target population) • Secondary objectives (setting the target population, choosing the diagnose method, etc.)

  25. Data analysis plan • Defining the study objectives: • To evaluate a diagnostic procedure • Main objective (to calculate the performance parameters of ultrasonography, sensibility, specificity) • Secondary objectives (setting the target population, defining the “golden standard”, etc.)

  26. Data analysis plan • Defining the study objectives: • To evaluate a therapeutic approach • Main objective (to compare the efficiency of laparoscopic cholecystectomy to the classical one) • Secondary objectives (setting the target population, setting the comparison criteria, etc.)

  27. Data analysis plan • Defining the study objectives: • The research of risk and/or prognosis factors • Main objective (to calculate the role of chromium in the etiology of pulmonary disease) • Secondary objectives (setting the target population, ensuring the compatibility between the study groups, etc.)

  28. Data analysis plan • Defining the working hypotheses: • To describe a health issue • The prevalence of pulmonary TB in Mures county is a public health problem • To evaluate a diagnostic procedure • Ultrasonography in gallstones diagnose is more sensitive and more specific than the clinical criterias.

  29. Data analysis plan • Defining the working hypotheses: • To evaluate a therapeutic approach • Laparoscopic cholecystectomy is easier supported by the patient than the classical one • The research of risk and/or prognosis factors • Chromium is a risk factor for pulmonary disease

  30. Data analysis plan • Sampling • To describe a health issue • Representative sample (qualitative and quantitative, transverse) • To evaluate a diagnostic procedure • Unrepresentative sample (qualitative and quantitative, transverse)

  31. Data analysis plan • Sampling: • To evaluate a therapeutic approach • Case-control data collection (retrospective, longitudinal) • The research of risk and/or prognosis factors • Case-control data collection (retrospective, longitudinal) • Exposed-unexposed data collection (prospective, longitudinal)

  32. Data analysis plan • Ensuring data quality: • Initial training of the data collectors (investigators) • Periodic verification of the data collection methods • Parallel data collection (if the data collection instrument allows it) • Investigators retraining

  33. Data analysis plan • Ensuring data quality: • Database development • Operator training • Data input into two parallel databases for comparison reasons • The development of validation programs for incorrect, extreme or missing values (aberrant, outliers, missing data)

  34. Data analysis plan • Hypotheses testing • Setting the data to compare • Setting the variable type which express medical data to compare • The correct choosing of statistical tests • The elaboration of “dummy tables” for each hypothesis to test

  35. Choosing statistical tests

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