TWO EXAMPLES
1. Discuss the arguments for and against screening for lung cancer
I will discuss this using the Wilson and Jungner criteria.
The disease
Lung cancer is serious and a public health priority because it is one of the
commonest fatal cancers in the UK today.
We believe we understand the natural history of the disease, which is one of
relentless progression and metastasis, though screening for other cancers (e.g.
breast) has revealed a proportion of hitherto unrealized spontaneous regression.
Also the stage at which metastasis occurs is crucial if screening is to be effective.
Early intervention is potentially beneficial. Screening trials in the 1960s showed
no benefit but the screening test then was plain chest X ray; there is more recent
evidence that screening with CT detects lesions at a curable stage, that is when
the lesion is still surgically resectable and before metastasis.
The test
The screening test must have adequate sensitivity and specificity. Sensitivity is
partly driven by the prevalence of the condition in the target population.
Screening for lung cancer should be targeted at a high risk group such as
smokers aged 50 or more.
Also sensitivity, the proportion of cancers detected, is determined partly by the
size of the tumour – screening may be 100% sensitive for 10cm lesions but only
50% for 1mm lesions.
The specificity of CT screening (the proportion of people free from cancer who
are correctly declared negative by the screening test) would need to be
established in formal trials. Low sensitivity results in false positives who have to
be investigated, wasting resources and possibly causing morbidity from
unnecessary thoracic surgery.
The test must be acceptable. Modern CT machines are simple and fast, and so
likely to be acceptable to patients.
The programme
Programme considerations include logistics, staffing, ethics and costs.
Logistics includes the availability of a list to invite the target population. If the
target population is identified simply by age there is no problem; if the
programme is aimed at smokers, then the completeness of GP smoking records
would need to established, though this should be high in the UK.
A key logistic question is whether we have sufficient CT capacity to run the
programme, and whether we have enough thoracic surgical capacity (surgeons
and theatres) to operate on confirmed cases.
The costs, and cost effectiveness of the programme would need to be worked
out. CT machines are expensive, and thoracic surgery is also expensive.
Another consideration is potential harms of the programme, particularly from
the radiation exposure in CT scanning.
------------------------------------------------------------------------------------------------2. Discuss the health effects of global warming
The World Health Organisation has defined health as a state of complete
physical, mental and social wellbeing.
Physical health
Global warming will melt the polar icecaps, raising sea levels everywhere. This
will lead to flooding in coastal areas, particularly in south east Asia where there
are several cities such as Kolkata which are coastal. Flooding in Bangladesh and
Thailand has caused great loss of life in recent years.
In addition global warming is thought likely to increase the frequency of extreme
weather such as droughts and storms. Crop failures will make things even worse
in areas which already suffer from malnutrition.
Warming may increase the range of insect vectors for diseases such as malaria
and typhus.
Increased sunshine in temperate areas may increase the incidence of sunsensitive cancers such as melanoma and squamous carcinoma of the skin, unless
preventive campaigns are effective. Heatwaves can increase mortality,
particularly among the frail elderly, as was seen in the Chicago heatwave.
On the other hand more sunshine may reduce the prevalence of vitamin D
deficiency and rickets which are increasingly prevalent in some parts of the UK.
Also, warmer winters may reduce excess winter mortality, which is a particular
problem in the UK (though its relationship to temperature is not entirely clear).
Mental health
Damage to crops and livelihoods, and the direct effect of destruction by storm
and flood will increase depression and anxiety. Even in England, severe flooding
in Bristol in the 1950s had a measureable adverse effect on mental health. The
current flooding in the Somerset levels is likely to have the same effect.
[.]
Social health
Displacement of large numbers of refugees is likely with drought or flooding. The
social consequence includes disruption of families as the more mobile members
(typically the young men) move to more affluent countries, while women,
children and old people remain in refugee camps.
On the other hand, shared adversity, if not catastrophic, can produce strong
bonding which may increase a sense of identity and social capital.