Block 5 Flashcards
What are the major antenatal/newborn screening programmes in the UK?
Downs syndrome
Infectious disease in pregnancy
Newborn bloodspot
Newborn hearing screening
What is the ‘Wilson and Jungner’/’National Screening Committee’ criteria for a screening program? 1968
Used by the UK national screening comitte to make decisions
- Important health problem
- Treatment must be available
- Facilities for diagnosis and treatment should be available
- Should be latent stage of the disease
- Should be a test/examination for the condition
- Test and treatment should be acceptable to the population (colorectal exam is unpleasant)
- Natural history of disease should be adequately understood
- Agreed policy on who to treat
- Should be cost effective
- Case-finding should be a continuous process
How do you classify test results?
True positive (TP) -
True negative (TN) -
False positive (FP) - dont have it but test incorrectly diagnoses
False negative (FN) - got disease and test missed it
Define sensitivity of a screening test and the equation used to determine it.
The proportion of people who have the disease that the test correctly detects
=TP/(TP + FN)
Dont miss too many cases
Define specificity of a screening test and the equation used to determine it.
The proportion of people who do not have the disease that the test correctly identifies as not having the disease
= TN/ (TN + FP)
Dont get too many false positives - need this to be very high for screening to be economically viable
What is the relevance of specificity and sensitivity?
Together, both measure test performance and are independent of the prevalence of the disease in the population.
This means:
If disease is present
Sensitivity tells you the probability the test will pick it up
Positive test
Neither model can tell the probability that you have disease, as this depends on the prevalence of the disease.
Define positive predictive value (PPV)
The probability that a person has the disease given that they have had a positive test result
= TP/ (TP + FP)
Define Negative predictive value (NPV)
The probability that a person does not have the disease given that they have a negative test result
= TN/ (TN + FN)
What issues are related to screening quality assurance?
Bias
1. Healthy screenee:
‘people who attend screening when invited live longer than those that do not, even if the screening test is useless’ People invested are more likely to be interested in living a healthy life
2. Length time bias:
Screening is better at detecting disease that develops more slowly/milder cases.
Slow developing diseases means that person has longer life as more likely to detect over time
3. Lead time bias:
Screening can detect illness earlier when it is more responsive to treatment and thus improve survival times
If survival time increases - is this because it was detected earlier?
How is child disability is defined in the UK?
Limiting long-term conditions/impairments that have a substantial impact on daily living
What is the prevalence of child disability in UK?
0.8 million disabled children and young people
(age 0 – 18 years) in UK
6% of all children
Remained stable over the past decade
What are the reasons put forward to explain increased prevalence of some conditions (autism/ADHD)?
Autism:
Increased prevalence likely due to increased awareness, new administrative classifications and diagnostic practices
ADHD:
Rise associated with increased recognition and diagnostic practices
What are the risk factors associated with child disability?
- Pregnancy outcomes (weight and premature)
- Sex
- Ethnicity
- Socio-economic disadvantage
- Parental behaviours
- Communicable diseases
- Unintentional injuries
What are the risk factors associated with child disability and pregnancy?
Low birth weight linked to a number of impairments (cerebral palsy, reduced cognitive function, epilepsy)
Improvements in neonatal care linked to increased survival rate for preterm births
Backed by evidence
What are the risk factors associated with child disability and sex?
Prevalence of all causes of disability is higher in boys in early years
By late teans prevalence for girls is similar to boys
Neurodevelopmental disabilities are more common in boys
May be linked with genetic differences - undiagnosed in girls?
What are the risk factors associated with child disability and ethnicity?
Limited evidence to suggest association
UK studies that control for socio-economic status found an increased risk for all-cause disability among children of mixed ethnicity and African/Caribbean origin only
Complex pattern for neurodevelopmental disability
- Rates of identification lower in 7-15 year olds in minority ethnic groups
- High rates of less severe intellectual disability among gypsy/Roma and traveller children of Irish heritage
- More severe forms of intellectual disability among Pakistani and Bangladeshi heritage
What are the risk factors associated with child disability and socio-economic disadvantage?
Prevalence of disability increases down the socio-economic gradient
Exposure to socio-economic disadvantage in early childhood is a predisposing factor for later onset disabling impairment/condition
Explanation:
Children from low SES households are more exposed to social/environmental risk factors in prenatal and early childhood
What are the risk factors associated with child parental behaviours?
Parental smoking:
(mainly maternal) linked to low birth weight, preterm birth and autism
Alcohol consumption:
Associated with growth before and after birth, educational outcomes, fetal alcohol syndrome
Unsupportive/unstimulating parenting:
Linked with some intellectual disabilities and conduct disorders
Many parental behaviours linked to poor health outcomes are linked to poor personal and household resources
What are the risk factors associated with child disability and communicable diseases?
Rubella during pregnancy
Measles and mumps in later childhood
Greatest risk for children not immunised
(not registered with GP, looked after children, some minority ethnic groups)
What are the risk factors associated with child disability and unintentional injuries?
Risk increases as children get older
At all ages, children from poorer households at greater risk
What interventions can be used to reduce child disability?
Primary prevention strategies:
Reduce socio-economic disadvantage
Improve material environments
Reduce exposure to environmental hazards
Reduce exposure to smoke
Promote safe alcohol consumption
Ensure adequate dietary intake of key nutrients
Immunisation against common diseases
Secondary prevention strategies:
Screening
Developmental assessments
Parents
Contact with other services (non-health)
What are the major young person/adult screening programmes in the UK?
Abdominal Aortic Aneurysm
Diabetic retinopathy
Breast cancer
Cervical cancer
Bowel cancer
What is Neuroblastoma?
Should it be screened for?
Childhood cancer of the nerve
50% survival rate increased to 97% when screening introduced
However death rate didn’t change as they were finding subclinical cases that never would have developed symptoms and would have self resolved - overdiagnosis and deaths as a result of treatment compications
Define overdiagnosis
Correct diagnosis of a disease, but the diagnosis is irrelevant because the disease will never cause symptoms within the patients lifetime.
Define overtreatment
Unnecessary treatment which does not improve health
Occurs in unessary screaning
Brest cancer screening - saves 1,300 lives a year but also 400 recieve un-necessary treatment eg radiotherapy
Should we screne for prostate cancer?
Lives saved from screening is minimal commpared to the harm done regarding sexual dysfuntion etc.
Do not offer in the UK - Can request a PSA test from dr
What is the popularity paradox of sceening?
The more you overdiagnose the more the popularity of the screening programme increases
Also occurs with awareness campaigns eg. Melonoma and incidental findings eg. chest x-ray
New diagnsosis increases but deaths haven’t decreased or increased
