Here’s an interesting one.
Based on national and local guidelines we aim for a blood pressure level of 140/85 mmHg.
We are a bit more strict in people with diabetes (140/80 mmHg).
The general consensus is that average home blood pressure should be lower than clinic blood pressure (130/80 if no diabetes and 130/75 with diabetes).
There has been pressure from the clever bods up on high to aim for much tighter bp control in people percieved to be at a higher risk of complications from a high blood pressure. For example people with diabetes, chronic kidney disease and established cardiovascular disease.
The logic goes something like this;
1. there is a continuous direct relationship between blood pressure and adverse cardiovascular events
2. the main aim in people with high blood pressure is to decrease their morbidity and mortality
3. lower the blood pressure
4. there is no clearly defined lower threshold of blood pressure which will do more harm than good, therefore see 1.
It was good to learn Arguedas et al have recently performed a Cochrane review.
Treatment blood pressure targets for hypertension
An extensive search was performed to look for randomized controlled trials comparing pateints randomized to standard or lower BP targets and their outcomes.
There were no trials comparing different systolic BP targets found. There were 7 trials comparing different diastolic BP targets. This was a total just over 22,000 people.
Look at the review (link) for the numbers, but essentially attempting to achieve lower targets instead of standard targets did not change;
- total mortality
- myocardial infarction
- stoke
- congestive heart failure
- major cardiovascular events
or
- end-stage renal disease
Aiming for blood pressure targets lower than 140/90 mmHg is not beneficial.
Phew! What a busy job I’ve landed. Into the 3rd week now and enjoying the job. Longer days are rewarded with a day off each week.
Anyway, expect a thinner smattering of blog posts because of this.
Two patients saw me last week clutching a Lifeline Screening leaflet. The post title is in large letters on the front cover of the leaflet.
Their vascular and heart rhythm package costs £139.00 and includes five tests. The leaflet goes on to explain;
1. Ultrasound scan of the carotid arteries.
to check for build up of plaque, a major cause of stroke.
2. 4-limb ECG.
which can identify AF, an intermittent condition which can increase the risk of stroke 5 times.
3. Ultrasound of the abdomen.
to check for an enlargement in the main artery (an AAA).
4. Ultrasound wrists and ankles.
an abnormal result may indicate a risk for peripheral arterial disease and increase risk of heart attack.
That’s only 4 test, but for an additional £10 you can also have;
5. Osteoporosis screening.
an ultrasound screen to check for the risk of osteoporosis.
“if signs are found, you can visit your GP who can help you determine the best steps for you”.
“when you know you are at risk, you and your GP will be empowered to take preventive steps such as lifestyle modifications, or medical management”.
Where, in the name of chocolate teapots, do I start?
This is all about using diagnostic clinical investigations as screening tests. Is the company aiming to improve the primary prevention of stroke in the population?
It feels like I’m standing at the wrong end of a telescope here and I would be concerned at the number of false positives produced by these investigations.
Lifeline Screening have “screened” over 75,000 UK residents so far. I wonder how much GP time that has created?
One of the reasons I am not confident in recommending laser eye surgery is that, as far as I know, the local ophthalmologists don’t “practice what they preach”. They don’t go for laser eye surgery themselves and choose to wear glasses.
It was interesting, therefore, to learn that 95% of male urologists over the age of 50 in the USA have had a PSA test.
Read more of the to screen or not to screen debate here.
Nice little post from a grumpy scientist, echoing my previous frustration on this topic.
“For myself I don’t really see why somebody complaining about the behaviour of doctors or the GMC, if that is what they are doing, why that should raise a question about their mental stability, unless anybody who wishes to criticise “the party” is automatically showing themselves to be mentally unstable because they don’t agree with the point of view put forward on behalf of the GMC or the party.”
I’ve recently been reading through ‘The Green Book’ again. Delving a little deeper than usual and reading some of the references too.
Do Multiple Vaccines Overwhelm or Weaken the Infant’s Immune System?
Offit et al determine the diversity of the immune response by estimating the number of vaccines a child could respond to at one time.
They make 5 assumptions;
1. 10 ng/mL of antibody is an effective concentration of antibody per epitope. An epitope is part of a macromolecule that is recognised by an antigen.
2. generation of 10 ng/mL of antibody needs approximately 10^3 B cells/mL. B cells recognise antigens, are stimulated to proliferate and produce large numbers of lymphocytes secreting an antibody to the antigen.
3. a single B cell clone takes one week to reach 10^3 in number.
4. each vaccine contains about 100 antigens and 10 epitopes per antigen (10^3 epitopes).
5. approximately 10^7 B cells are present per mL of circulating blood.
If you are still with me this means that each child has, theoretically, the capacity to respond to about 10,000 vaccines at any one time.
(10^7 B cells per mL divided by 10^3 epitopes per vaccine)
This is likely a conservative estimate as many vaccines contain fewer than 100 antigens. For example, the Diphtheria and Tetanus vaccines each contain one antigen.
Looking at the first 12 months of the schedule for the UK’s routine childhood immunisations, there are 8 injections comprising about 20 vaccines.
Even if these 20 vaccines were all given at the same time, they only “use up” 20/10000 = 0.2% of the capacity of the immune response.
B cells and T cells are also constantly being replenished increasing the ability of the immune response further.
Pet Hate
Offit et al make the 5 assumptions by referring to this paper. My Athens account does not cover this publication. I would love to look at it but I’m not paying over 30 US dollars for the “privilege” of 24-hour access. The inaccessibility of research (the reference is from 1990!) is a pet hate of mine.
Take-home message
Infants have the capacity to respond to an enormous number of antigens.
Understanding Uncertainty has an absolutely brilliant animation that spins risk in many different ways. The link also allows you to adapt it to your own data.
This is much more clear than my previous attempts at explaining risk and I urge you to try it out.
