Drug Use Measures Lecture Notes

Epidemiology

• Epi: among
• Demos: People
• Logos: Study
• Epidemiology is defined as the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to control health problems.
• There are three closely interrelated components: distribution, determinants, and frequency, encompassing all epidemiological principles and methods.

Outcome Measures

• Measuring outcomes is an important component for the management of individual patients by collectively comparing care and determining effectiveness.
• The use of standardized tests and measures early in an episode of care establishes the baseline status of the patient/client, providing a means to quantify change in the patient's/client's functioning.
• Outcome measures, along with other standardized tests and measures used throughout the episode of care as part of periodic reexamination, provide information about whether predicted outcomes are being realized.

Goals of Measuring Clinical Outcomes

• Improve the patient experience of care
• Improve the health of populations
• Reduce the per capita cost of healthcare

Methods of Outcome Measurement

• Statistical Methods
• Drug Use Methods

Per Capita Health Expenditure in Selected Countries in 2022 (in U.S. dollars)

• United States: $12,555.3$
• Switzerland: $8,049.1$
• Germany: $8,010.9$
• Norway: $7,898$
• Netherlands: $7,357.6$
• Austria: $7,275.4$
• Belgium: $6,600$
• Australia: $6,596.5$
• France: $6,516.6$
• Sweden: $6,437.7$
• Luxembourg: $6,436.1$
• Canada: $6,319$

AB-PMJAY Scheme

• A significant number of beds have been empanelled under the scheme.
• 7,005 hospitals have more than 50 beds.
• 3,196 hospitals have more than 100 beds.
• 435 hospitals have more than 500 beds.
• 234 Medical Colleges are empanelled.
• Many corporate hospitals are also empanelled.

Drug Use Measures

• It includes the pattern of use of drugs for a specific disease/in a group of people. Different types of drug use measures are:
  1. Monetary units
  2. Number of prescriptions
  3. Units of drug dispensed
  4. Defined daily doses (DDD)
  5. Prescribed daily doses (PDD)
  6. Medication adherence measurement

Monetary Units

• It is the most common and generally used practice in the estimation of drug use to quantify the value of medicine in monetary units like rupees, dollars, etc.
• It helps to find the percentage of the financial burden for individuals, families, societies, organizations, or governments for drug use.
• Applicable for comparisons at various levels from person to global.
• Monetary units are convenient and can be converted to a common unit, which then allows for comparison.

Economic Burden of Dengue Illness in India from 2013 to 2016

• India had about 53 million symptomatic dengue cases in 2016.
• The overall cost of dengue in 2016 was about US$5.71 billion, with 14.3$\frac{Item\ used \times Amount\ of\ drug \per\ item}{DDD}

Major Drug Groups Without DDDs

• Topical products
• Sera
• Vaccines
• Antineoplastic drugs
• General/local anesthetics
• Ophthalmological / ontological
• Allergen extracts
• Contrast media

More on DDD

• The DDD is a unit of measurement and does not necessarily correspond to the recommended or Prescribed Daily Dose (PDD).

• Therapeutic doses for individual patients and patient groups will often differ from the DDDs, as they will be based on individual characteristics such as age, weight, ethnic differences, type and severity of disease, and pharmacokinetic considerations.

• Advantages: Its usefulness in working with readily available drug statistics and allows comparison between drugs in the same therapeutic classes.

• Disadvantages: Doses may vary widely (e.g., antibiotics).

Applications of DDDs

• Examine changes in drug utilization over time
• Make International comparisons
• Evaluate the effect of an intervention on drug use
• Document the relative therapy intensity with various groups of drugs
• Follow the changes in the use of a class of drugs
• Evaluate regulatory effects & effects of interventions on prescribing patterns

Prescribed Daily Doses (PDD)

• PDD is defined as the average dose prescribed according to a representative sample of prescriptions.
• The PDD can be determined from studies of prescriptions, medical or pharmacy records, and it is important to relate the PDD to the diagnosis on which the drug is used.
• The PDD will give the average daily amount of a drug that is actually prescribed; Useful for validating the defined daily dose (DDD).
• Pharmacoepidemiological information (e.g., sex, age, and mono/combined therapy) is also important in order to interpret a PDD.
• PDDs vary according to:
  • Illness treated
  • National therapeutic tradition
  • Between different countries; For example, the PDDs of an anti-infective may vary according to the severity of the infection.
• There are also international differences between PDDs, which can be up to 4 or 5-fold higher/lower. Eg: PDDs in Asian populations are often lower than in Caucasian populations.

Medication Adherence

• Medication Adherence: The patient's conformance with the provider's recommendation with respect to timing, dosage, and frequency of medication-taking during the prescribed length of time.
  • It is a factor that determines the therapeutic outcomes in a patient suffering from chronic illness/diseases.
• Compliance: How well the patient follows the instruction of when and how to take the medication.
• Persistence: Duration of time patient takes medication, from initiation to discontinuation of therapy

Causes of Medication Non-Adherence

• Socio-economic: Poor socioeconomic status, illiteracy, lack of family or social support, lack of financial resources, busy work schedules, high cost of medication.
• Health care system related: Relationship of doctor-patient, poor or lack of proper communication regarding the beneficial effect of taking medication, instructions for use and side effects, poor medication distribution.
• Therapy related: Complexity of medical regimens, duration of treatments, lack of immediate benefit of therapy and treatment interferes with lifestyle.
• Condition related: Severity of symptoms (chronic illness requires long term drugs administration OR few or no symptoms).
• Patient related: Impairments such as visual, hearing and cognitive impairments and swallowing problems, lack of motivation, apprehension about possible adverse side effects, stress, anxiety.

Problems Linked with Medication Non-Adherence

• Therapeutic failure
  • Increased exposure to toxicological effects of drugs
  • Recurrence of disease
  • Unable to cure the disease and disease progression
  • Leads to complications of disease
• Economic loss to the patient
• Low quality of life
• Patients death

Measurement of patient adherence

Direct Measurement

• Home finger prick sampling.
• Biological markers
• Directly observed therapy

Indirect Measurements

• Self-report measures (using questionnaires)
  • Morisky's medication adherence scale
  • Medical outcome adherence study scale
  • Brief Adherence Rating Scale
• Electronic Adherence monitoring

Rates, Ratios, and Proportions

• Rate: Measures the occurrence of an event or disease in a given population during a given period (one year).
  • Examples: Birth rate, growth rate, accident rate.
  • Usually expressed per 100 or per 1000 population.
  • It has a time dimension, whereas a proportion does not.
  • Rate = \frac{Numerator}{Denominator} \times Multiplier
  • Death rate = \frac{No\ of\ deaths\ in\ one\ year}{Total\ mid\ year\ population} \times 1000
• Ratio: The value obtained by dividing one quantity by another (X/Y).
  • Male to female ratio.
  • A ratio often compares two rates, such as death rates for women and men at a given age.
  • Numerator is not part of the Denominator.
• Proportion: A part/share or number considered in comparative relation to a whole.
  • Usually expressed as a percentage (%)
  • Numerator is always part of the denominator.

Ratio Example - Infant Mortality Rate

• Goa: 1:495 doctor population ratio, 11 infant mortality rate
• Kerala: 1:811 doctor population ratio, 12 infant mortality rate
• TN: 1:789 doctor population ratio, 22 infant mortality rate
• Odisha: 1:2500 doctor population ratio, 57 infant mortality rate
• UP: 1:3316 doctor population ratio, 57 infant mortality rate
• MP: 1:2600 doctor population ratio, 59 infant mortality rate

Special Incidences

• Crude Death Rate (CDR): Number of deaths from all causes, per 1000 estimated mid-year population in one year in a given place.

  • CDR = \frac{No\ deaths\ during\ one\ year}{Mid\ year\ population} \times 1000

• Specific Death Rate: Cause-specific death rate (e.g., disease death rate, road accident), age-specific (IMR, Child Mortality rate), sex-specific death rate (MMR/female), period-specific death rate (Death in May).

• Case Fatality Rate: Percentage of particular cases dying during a particular disease epidemic.

  • CFR = \frac{No\ of\ deaths\ due\ to\ cholera}{Total\ No\ of\ cholera\ cases} \times 100

• Proportional Mortality Rate: Proportion or % of deaths due to a particular cause out of total deaths.

  • Under 5 proportional mortality rate = \frac{Number\ of\ deaths\ below\ 5\ years}{Total\ number\ of\ all\ deaths} \times 100

Survival Rate

• Percentage of the treated patients remaining alive at the end of 5 years treatment.
  • Survival Rate = \frac{Survival\ pts\ alive\ at\ the\ end\ of\ 5\ yrs}{Total\ number\ of\ pts\ treated} \times 100
• Standardized Death Rate (Adjusted Death Rate): CDR cannot be useful for comparison. Death rate needs to be standardized for comparisons. Standardization can be done by adjusting death rate age-wise, also can be done sex/race-wise.

Prevalence

• The amount of a disease at one particular point in time
• The proportion of people who have the disease
  • There are two types of prevalence known as the:
    • Point Prevalence
    • Period Prevalence
  • Prevalence\ (%) = \frac{number\ of\ people\ with\ disease}{number\ of\ people\ in\ the\ population} \times 100\%.

Incidence

• Two definitions
  • Incidence\ proportion = \frac{number\ of\ new\ cases\ of\ disease}{population\ without\ disease\ at\ baseline} \times 100\%.
  • Number of new cases of disease in a specified time period
• Cumulative Incidence
  • Cumulative \ Incidence = \frac{number\ of\ new\ cases\ of\ disease}{Number\ of\ persons\ at \ risk\ the\ beginning\ of\ that\ time\ period}
  • Incidence\ rate \ (incidence\ density) = \frac{Number \ of\ new\ cases\ of\ disease\ in\ a\ specified\ time \ period}{person-time\ at\ risk}$$

Person Time

• It is the sum of time each person remains at risk for the health outcome and under study observation
• It can be expressed in terms of person years, person months, person days
• This is used because follow up period does not need to be uniform for each participants
• Person time of a population-sum of the times of follow up for each participants in that group