Other bits Flashcards
what is IRIS
immune reconstitution inflammatory syndrome
Seen in some cases of immunosuppression
when the immune system begins to recover e.g. when ARVs initiated
The immune system then responds to a previously acquired opportunistic infection with an overwhelming inflammatory response
This paradoxically makes the symptoms worse
What are the notifiable diseases
Acute encephalitis Acute infectious hepatitis Acute meningitis Acute poliomyelitis Anthrax Botulism Brucellosis Cholera Diphtheria Enteric fever (typhoid or paratyphoid fever) Food poisoning Haemolytic uraemic syndrome (HUS) Infectious bloody diarrhoea Invasive group A streptococcal disease Legionnaires’ disease Leprosy Malaria Measles Meningococcal septicaemia Mumps Plague Rabies Rubella Severe Acute Respiratory Syndrome (SARS) Scarlet fever Smallpox Tetanus Tuberculosis Typhus Viral haemorrhagic fever (VHF) Whooping cough Yellow fever
Who should be offered the HPV vaccine
males <45yrs if MSM or HIV +ve or immunocompromised
Trans-men or trans-women who has / is likely to have receptive anal sex if ≤45 years
Consider in F aged 9 - 26 if a victim of sexual assault and have not started or completed the course
Vaccination schedule for HPV
0, 1 and 3- 6 months - if aged 1 5 - 26 = 3 dose schedule
0, 6 - 12 months if 9 - 14 years = 2 dose schedule
types of observational study.
2 types of observational study:
descriptive observational studies
analytical observational studies
different types of descriptive observational studies
Case report
Case series
Cross-sectional
advantages and disadvantages of case reports
Definition - A case report is a profile of an individual patient that has experienced a particular outcome which is reported in detail.
Advantage = useful to document rare outcomes.
Disadvantages = not possible to draw any inference from a case report as it refers to only one observation
advantages and disadvantages of case series
Definition = includes a number of patients who have all experienced the same, particular outcome.
Advantage = may suggest a possible hypothesis to investigate with an analytical, observational study or an experimental study
Disadvantage = Although more than one observation - it is not sufficient numbers to draw any robust conclusions.
advantages and disadvantages of cross sectional descriptive studies
Definition = A cross-sectional study involves observing a subset of the population at a single point in time - in terms of the frequency and characteristics of an outcome of interest
Advantage = Robust relationships can be identified if a sufficiently large number of people are studied.
Disadvantage = cannot establish causality with a cross-sectional study. No information about the sequence of events is gained. Association only
Types of analytical observational study
4 types of analytical observational study:
Ecological studies
Cohort studies (also known as longitudinal studies)
Case-control studies
Cross-sectional studies
advantages and disadvantages of an ecological study
An ecological study is one in which the unit of analysis is a population rather than an individual
Advantages = economical / quick / tend to use existing, aggregate data.
Disadvantages = regarded as inferior to individual-level study designs as they only provide indicative rather than compelling evidence of causal relationships because they are susceptible to ecological fallacy
what is a cohort study
individuals with a particular characteristic are followed over time + compared with a group who do not have the characteristic, for the occurrence of an outcome of interest.
usually prospective (can be retrospective) involve collecting data on at least two time points over the study period
advantages and disadvantages of a cohort study
Advantages = useful to study relatively rare outcomes
Recall error can be minimised - due to collection of data at regular intervals
Disadvantages = Expensive
Time-consuming
Sensitive to attrition
What is a case-control study
case-control study = comparing a group of people who experience the outcome with a group of individuals who do not experience this outcome
Risk factors preceding the outcome are compared between groups
Often selecting matched controls
advantages and disadvantages of a case-control study
Advantages = Relatively economical Relatively quick Can investigate a wide range of factors Useful for studying rare diseases
Disadvantages =
Prone to ‘selection bias’ of cases and controls
Prone to ‘observer bias’
Difficult to determine sequence of events
Cannot obtain estimates of disease incidence
what is the CONSORT statement
an evidence-based, minimum set of recommendations for reporting RCTs.
A standard way for researchers to prepare reports of their trial findings
Facilitating complete and transparent reporting
Aiding critical appraisal and interpretation
define prevalence
Prevalence is used to measure how commonly a disease or condition occurs in a population.
Calculated as the number of cases in a population at one point in time divided by the total number of persons in the population at that time
aka ‘point prevalence’
prevalence is a proportion
Factors influencing prevalence
The frequency with which the cases occur and are identified
The average duration of the condition (i.e. time to either recover or die from the condition)
Define incidence
Incidence = used to measure the number of new cases of a condition that develop in a population at risk during a specified time interval.
Where the denominator is person-time at risk then it is referred to as the ‘incidence rate’
Incidence rate = the number of new cases during a specified time interval divided by the person-time at risk (and so free from the disease) during the study period.
How can the relationship between incidence and prevalence be approximated
Prevalence = incidence x average duration
what is risk ratio
The ratio of the risk of having the outcome of interest if in the exposed group
compared to the risk of having the outcome of interest if in the unexposed group
A/(A+C) / B/(B+D)
what is the odds ratio
The ratio of the odds of having the outcome of interest if in the exposed group
compared to the odds of having the outcome of interest if in the unexposed group
(A/C) / (B/D)
what does a relative risk of <1 mean
Relative risk value of less than 1.0
= an inverse association
= a decreased risk among the exposed group
i.e. the exposure is protective
what does a relative risk of 1 mean
Relative risk = 1.0
indicates the incidence of disease in the exposed and non-exposed groups are the same
No association between the exposure and the disease
what does a relative risk of >1 mean
Relative risk > 1.0
Indicates a positive association
An increased risk among the exposed group
what is the difference between register based and opportunistic screening programmes
Register-based = where eligible individuals in a defined population are identified and proactively invited for screening using a register
Opportunistic = individuals that come into contact with services are assessed for their eligibility for screening and then invited to be tested.
Pros and cons of opportunistic screening
Pros - avoids cost of register
avoids potential breach of confidentiality
cons - unlikely to reach all those at risk
the hardest to reach may be most at risk
define sensitivity
Sensitivity = A fraction
Those with the disease correctly identified by a positive test.
define specificity
specificity = A fraction
Those without the disease correctly identified by a negative test.
Define positive predictive value
those with a positive test
who actually have the disease
Define negative predictive value
those with a negative test
who do not have the disease
