Medical Evidence

In the second of a two-part series, Jim Ring looks at what evidence means to different people

Scientific evidence is often difficult to interpret, in medicine in particular. ‘An Unfortunate Experiment’ was the title given to the treatment for some women after screening for cervical cancer. In this case science was considered by the legal profession and apparently found wanting. The doctor involved was castigated and publicly humiliated for experimenting on humans. But no real experiments were ever done; it appeared he did not understand scientific methodology. Neither did the journalists and legal people involved. The point is that no proper controls were used so it was very poor science.

Were the women disadvantaged? It is difficult to tell, but many were certainly outraged. It generally escaped notice that the surgeon was responding to public pressure for less radical surgery and that a group of patients involved seem to have had on average a slightly better outcome than the norm.

One of the most unfortunate ideas that came out of the long legal case was the emphasis on privacy for the individuals involved which implied their records should not be available for medical study. There is a difference between privacy and anonymity. It is very important to explain to those involved in medical procedures that for medicine to progress it is essential to collect data. Women appeared on TV complaining bitterly that they had been used in an experiment without their consent. But all good medicine is experimental.

We are not much closer to determining whether mass screening for cervical cancer does improve the chances for the screened population and now we have another scandal in New Zealand. Public expectation of screening programs is far in excess of what they can deliver. Efforts to sue Dr Bottrill, and compensation claims from ACC, seem to imply that patients think a false negative reading is necessarily medical error. Women have appeared on TV claiming their lives have been devastated because they had a false negative. Surely this is wrong; they are rightly upset but this is because further tests show a medical problem. Of course some who died might have been saved if an early intervention had resulted from a correct positive reading; however this does not seem to be the main thrust of their complaint.

False Negatives vs False Positives

It is possible to reduce the number of false negative readings at the expense of an increase in the number of false positives. This may seem desirable but there is a cost. In Britain large numbers of women in a screening project reacted very badly to finding they might have a ‘pre-malignant’ condition. This included some members of the medical profession. There is a clear indication that patients were not well informed before screening.

Patients involved in any medical procedure are supposedly asked for their ‘informed consent’. It seems now obvious that ‘informed consent’ is largely lacking during mass screening for both cervical and breast cancer. Several of those involved in the public hearing are surprised to find that screening is less than 100 per cent accurate. All mass screening procedures are likely to have a high error rate as they are designed to be rapid, cheap and simple; leading to more precise testing if there is a positive result. Is a large and expensive inquiry, using legal methods, a suitable way of investigating scientific questions?

Cervical cancer, unlike breast cancer, is strongly correlated with environmental factors. The former is very rare in the general population with a relatively high incidence in a certain sector. However it is politically incorrect to target the high-risk population for screening because the risk correlation is with such factors as poverty, poor hygiene and sexual promiscuity.

A recent case of a gynaecologist accused of misconduct raises some interesting issues. The unfortunate patient would seem to be outside the high-risk group for cervical cancer, thus an assumption may have been made that the correct diagnosis was very unlikely. But no physical vaginal examination was made. Feminist literature once strongly criticised the medical profession for over-use of this procedure, which one writer described as ‘legalised rape’. It would be interesting to know the rate at which this procedure is used today compared with, say, 30 years ago. Is the medical profession responding to crusades in a way that disadvantages patients?

Objections to trials

Medical ethicists – now a profession – have objected to various drug trials saying it is unethical to provide some patients with a placebo that will not improve their condition. This is in effect a claim to certain knowledge – that the drug being trialed is the ideal treatment. Patients receiving a placebo are not disadvantaged when the new drug may do more harm than good. We can sympathise with terminally ill patients who know that they will die in the absence of treatment and where anything seems a better bet than a placebo. But it is essential that drugs be properly tested before being used routinely.

Experiments have even been done in surgery. In 1959 patients were randomly assigned, but all prepared for surgery and the chest cavity opened. Only then did the surgeon open an envelope and follow the instruction; either to perform the procedure or immediately close the chest. Although some ethicists have objected (one stated that such surgery would never take place in the UK), a double-blind study of brain surgery was recently done in the US. Not only did it pass an ethics committee but patients welcomed the chance to take part even though it involved drilling the skulls of both real and placebo patients. In this case there was considerable improvement in those under 60 who had the real operation.

This indicates people may be willing to give consent to risky experiments providing they are given good information.

Most evidence in medicine comes not from experiments but from epidemiology. This requires the collection of huge amounts of data and sometimes produces conflicting results. Two populations, which differ only in the factor under investigation, should be matched and this is difficult to achieve. Recently, in a world-wide study, doubt has been cast on the efficacy of breast-cancer screening. New analysis purports to show that when populations are matched correctly, the screened population has no better chance of survival than an unscreened population.

Demands for safety

Some demand that all medical procedures should be ‘safe’, though curiously this is not required of alternative medicine. Suppose a new drug has fatal consequences for one patient in 100,000. It is quite likely that this will not be discovered during testing. Should such a tiny risk preclude the use of a drug that gives significant benefits to the vast majority of patients? New medicines are introduced when they show a clear advantage over a placebo. When very large numbers are involved in a study it is possible for a drug to show a significant advantage, yet not be worth introducing. Significance is a technical term and it is possible to find an advantage of only 0.1% is ‘significant’, though it may not be worth taking such a product.

It was this confusion that bedevilled early experiments on ESP. Rhine in America and Soal in England recorded the success of subjects guessing unseen cards. The experimenters wrongly assumed controls were unnecessary; instead they compared guesses with a theoretical chance result. A few subjects scored correct guesses at slightly more than chance and because huge numbers of guesses were involved, statistical tests showed these results had ‘significance’. That is, there was a huge probability that the guesses were not simply ‘lucky’.

Enthusiasts then made the enormous leap to say that because the guesses were not due to chance they must be due to a previously undiscovered human faculty, extra-sensory perception or ESP. Disinterested observers, not just skeptics, should have concluded that other explanations, such as poor experimental design, badly recorded results, fatigue, or just plain cheating were more likely. A great deal of time, money and effort was spent pursuing this will-o’-the-wisp.

Legal Evidence

Skepticism is very much concerned with assessing the quality of evidence in support of a particular claim. But evidence means different things to different people. In the first of a two-part series, Jim Ring examines the legal profession’s view of the matter.

Our knowledge of the world is never certain, so what should count as evidence that a claim is true? For many people trained in science the legal system contains some very strange anomalies. Material can be accepted as evidence in court even though it would be given no weight at all in a scientific context.

People are sometimes imprisoned because juries are prepared to accept the unsupported word of witnesses. David Dougherty was in jail three years for raping a young neighbour. She said he had done so. No other evidence pointed to a conviction; tests on DNA were inconclusive. Later, better tests indicated that the girl had had sex with a man other than Dougherty.

Peter Ellis (the Christchurch crèche case) was jailed because some small children told the court he had done dreadful things. The same children told questioners that some women had done dreadful things, but they were not believed. They also told stories about Ellis that could not possibly be true and these were edited out of the story put to the jury.

In science experiments a control is a most important feature. Unfortunately controls are generally ruled inadmissible by judges. In the Ellis case there was an excellent control for the children’s credibility. How reliable were the children’s stories about the women, and how reliable were their stories about Satanism and black magic?

Eyewitness accounts are given great weight in our justice system; yet in the US it has been estimated that mistaken eyewitness evidence is responsible for about 80 per cent of the wrongful convictions that occur. The trial of Scott Watson (Marlborough Sounds New Year murders) was unusual in that eyewitness evidence was treated in a different manner. The prosecution held that part of the evidence of one of their own witnesses was in error. He had a distinct memory of a two-masted yacht; the prosecution argued that he must have seen one with a single mast. In future will eyewitness evidence be treated as less conclusive?

In New Zealand a cell-mate can claim to have received a confession of guilt from a person awaiting trial. That such an anecdote can be accepted as evidence in court would be beyond belief – except it happens!

It was reported last year in the UK that a judge instructed a jury not to bother about statistics and just to use their common sense (let us hope this report was inaccurate). But common sense is not a reliable guide in complex matters. Science and statistics often produce results that are quite counter-intuitive.

A conviction is only supposed to take place when evidence is beyond all reasonable doubt. In New Zealand people are sometimes convicted in spite of reasonable doubt.

Salting Away the Profits

The marketing of sodium chloride should be taken with a pinch of salt

Sodium chloride is a very simple chemical and cannot decay. Excess is harmful though it is an essential part of our diet. These days many people seem to believe that some forms are better than others.

Years ago an idea developed that all white foods were bad: bread, sugar, milk, salt. Similarly it was held that all refined substances were bad: (because they were unnatural), while food additives were worse (though of course diet supplements do not count).

Table salt is white, it is refined, anti-caking agent is added to prevent clogging in damp weather, and a tiny amount of potassium or sodium iodide is added for health reasons. Thus it offends against a host of popular prejudices.

Many people’s diet is short of the essential element iodine, which is added to salt to prevent deficiency. In particular, without sufficient iodine, children’s brains will not develop properly and they suffer a form of mental retardation called ‘cretinism’. It has been claimed that non-iodised salt is better for preserving food (though I know of no scientific justification for this), so this is available in bulk packs.

In most countries salt is obtained from underground deposits, either by mining or by dissolving it in water. It is not generally extracted from seawater because this is so dilute that huge amounts of energy are needed to evaporate such large quantities of water. A dry climate at low latitudes allows solar energy to be used, but large areas are needed so land needs to be cheap.

These requirements are marginally met at Grassmere in the Awatere valley, Marlborough, where evaporation exceeds precipitation in nine months of the average year. A long-established solar salt industry is a prominent feature, visible to travellers between Picton and Christchurch. However the suitable area is limited and New Zealand has always imported salt.

Solar salt is of sufficient purity for most purposes but not all. Vacuum salt is more highly refined and is produced both at Grassmere and Mt Maunganui; the latter uses imported salt as feedstock.

A fad starting in Europe held that sea salt was healthier than other kinds, being ‘more natural’, and it was believed this came as large crystals. Fashionable restaurants provided salt grinders, which held large crystals of sodium chloride, rather than the old dispensers of fine crystals in a shaker. One advantage of sea salt, it was argued, was that it was ‘more salty’ and therefore healthier because less would be needed.

It is possible that relatively large crystal fragments have a more vigorous assault on the palate, however most salt is added in cooking, and in solution all salt is equally ‘salty’. Salt ions have no memory so do not know what size crystal they inhabited.

The underground deposits in Europe are remains of dried-up seas, so all their salt is ‘sea salt’; while in NZ the cheapest form of table salt is locally produced, and made directly from sea water. Furthermore it is not really ‘highly refined’.

It may be of concern that some parents refuse to use iodised salt, and so expose their children to a risk of iodine deficiency. It is claimed that in New Zealand, iodine intake has been dropping for twenty years. In the 1990s intakes twice fell below internationally recommended levels (NM 17th May Report quoting Elizabeth Aitken in NZ Dietetic Association Journal).The decreased use of iodised salt in our diet is to be deplored.

On Sale Now

I had a look at what is available in Nelson and the results were quite interesting. The cheapest salt available was Skellerup Marlborough in bulk packs at $0.80 per kg. It could be bought either iodised or non-iodised. Prices for similar quality in other brands ranged up to $1.00.

Salt in dispensers was naturally dearer because of the packaging; the price range was $2.10 – $3.60 per kg.

The dearest salt was Maldon Sea Salt from Essex, England, declared to be ‘Unrefined and Natural’. Various NZ writers on health and food have touted this as a superior product. It needs to be good, as the price was $38.75 per kg.

Other imported products were:

Celtic Sea Salt produced in Brittany and packaged by Lotus in Australia priced at $13.46 per kg. This claimed to be ‘Hand harvested and Unbleached’ (whatever that means). It consisted of large brownish crystals and was very sticky. The pack carried an analysis showing it to be only 83% sodium chloride with 7% water. Other elements (found in seawater) amounted to around 3% so what else the stuff contained we do not know.

Also available was Lotus Australian Sea Salt. This was only available as a fine grade; but a relative bargain at only $2.50 per kg.

Some small New Zealand firms were selling salt.

Solar Sea Salt was from Kaiora Organics, Napier and certified by Bio-Gro (organic salt is a splendid idea). These large crystals at $8.81 per kg were ‘unrefined, unwashed’.

A Nelson firm provided ‘Safe Earth Unprocessed Sea Salt, “The way Nature created it” Not altered, Not refined, No additives, Natural Minerals retained. Bio-Gro certificate currently being sought’.

They have a leaflet that is a mixture of good sense and outrageous claims. Stating that salt cannot be organic, but also; ‘unprocessed sea salt is a natural antihistamine’. In a health shop it was $18.00 per kg for both large crystals and normal grade. At a supermarket it was $15.88 per kg; still hardly a bargain.

Presumably for legal reasons the pamphlet refers to an overseas website rather than making direct claims – nevertheless under ‘Prevention and Cure’ it manages to refer to most human diseases except cancer, including such refractory problems as ‘Altzheimer, Multiple sclerosis, and Insulin Independent Diabetes’ (sic).

It also includes the delightful thought; ‘Without sufficient water to wet all parts equally, some parts of the body will not receive the vital elements that water supplies’.

Bargain price

Large crystals of Empire Rock Salt by Hansells NZ were at a bargain price ($1.25) in one supermarket. Apart from the claim ‘no additives’, there was no further information. Without labelling on the packet, this was of dubious legality.

The large companies are also in on the act and their products labelled ‘Sea Salt’ are much cheaper than those sold by the small companies; though more expensive than their own sea salt without the label. This is a truly wonderful way of adding value. Saxa and Cerebos have fine ‘Sea Salt’, not iodised but with added anti-cake which sells at a range of $1.20 – $1.55 per kg depending on the supermarket. This is generally around 20-35c more than their similar (possibly identical) product not labelled ‘Sea Salt’.

But in one Supermarket I found Cerebos Sea Salt as large crystals at $1.20 per kg. It is more expensive to produce large crystals so this is very reasonable. It makes ‘Maldon Sea Salt’, essentially the same product but 3000% dearer, look rather overpriced.

The Spectre of Kahurangi

Goethe’s Faust is a tale of the supernatural. According to a famous passage, on Walpurgisnacht a witch’s sabbat was celebrated on top of the Brocken, a mountain in the Black Forest. Old maps show this point circled by witches on broomsticks. Although probably not a very ancient tradition, it grabbed the imagination of 19th century romantics. They claimed at certain times magical visions could be seen from the peak. Even though no witches were visible on the mountain, gigantic shadowy figures were projected onto the clouds; the Spectre of the Brocken.

According to the Encyclopaedia Britannica “this phenomenon is often observed on mountain peaks” but even the non-supernatural explanations seem unbelievable. According to the Britannica “When the sun is low, shadows cast by the sun become magnified and seemingly gigantic silhouettes are cast on the upper surfaces of low-lying clouds or fog below the mountain.”

A later entry is contradictory: “The apparent magnification of size is an optical illusion that occurs when the observer judges his shadow on nearby clouds to be the same distance as faraway objects seen through gaps in the clouds.”

So is the magnification real or an illusion? As the sun’s rays are practically parallel, any shadow cast by the sun remains the same size as the object. Thus a shadow at even a modest distance from the observer can only seem small. In justification Britannica mentions the common sight of an aeroplane’s shadow cast on clouds beneath, but a jumbo jet casts a decent sized shadow, a human sized shadow would be insignificant.

In spite of many literary references (De Quincey for example) first-hand accounts of “the Spectre” by first-rate observers seem non-existent. (Does any reader know of any?). But some accounts state that the figures seem frightened of the observer and rush away as soon as they are seen.

The whole thing seems ridiculous, or so I thought until I saw the phenomenon myself in New Zealand. In fact I have observed this effect twice-which considering the time I have spent in the mountains, implies it is a relatively rare event.

The first occasion was when climbing a ridge above the Wangapeka River in what is now Kahurangi National Park. The sun rose over another ridge behind us and gigantic shadow figures appeared on the hillside across the valley. Before I had fully grasped what was happening they had shrunk down to normal size, where they were just visible. At least that explained the accounts of figures “rushing away”, they simply got smaller, and very rapidly too.

The explanation was quite obvious to anybody with some knowledge of optics; light is refracted when passing over an edge. The first gleam of sunlight over the ridge was bent into a widening beam that produced a huge shadow as effectively as a point of light projects an enlarged shadow onto a screen. The bush-clad hillside opposite us acted as a screen on which we could see the projection. But as the sun rose, the refraction diminished until enough of the sun was visible to produce the normal parallel rays with which we are familiar. So the initial large shadow quickly shrank to normal size.

Was this illusion awe-inspiring? Was it even an illusion? Were we frightened? Was it immediately obvious that we were observing our own shadows not supernatural entities? Well no, no, no, and yes. My wife, the complete skeptic, summed up, “Why make a fuss about shrinking shadows?”

I am confident that I can explain the reports of run-away shadows in mountain regions. The conditions necessary for observing this phenomenon seem to be that the sun must rise over a not too distant sharp edge, the air should be still and very clear. The observers be on a minor peak or ridge, and the projection be onto a fairly plain surface.

Does this explain the “Spectre of the Brocken” better than the Encyclopaedia? Well to be honest, no. The Brocken is the highest mountain around. So how could the sun rise over a sharp edge unless other peaks are very close? I doubt that clouds can ever have sufficiently sharp edges to produce the effect.

Perhaps the Spectre of the Brocken is as real as the reports there of witches, while its magical reputation has seen it acquire stories of phenomenon that are real in other mountainous areas.

References

Bob Metcalfe (Forum NZ Skeptic 54) seems to be calling for a change in editorial policy on footnotes and references. This has been consistent throughout the history of this society and any change would completely alter the character of this journal. What do members want? I thank him for his apology. Anything that increases feedback on articles in NZ Skeptic and the numbers of letters in Forum is to be welcomed.

Continue reading

Organic Means What?

The Swedish chemist Berzelius coined the term ‘organic’ for substances that could only be made by living organisms and not synthesised by humans. His German friend Wöhler synthesised urea in 1828 proving Berzelius wrong, there was no such distinction. Another brilliant German chemist, Liebig, then used ‘organic’ to mean carbon-compound chemistry, extending this to include the chemistry of living organisms- so beginning biochemistry.

Continue reading

A Brief History of Skepticism

Around 300BCE there started a school of Greek philosophy called Skepticism. It continued for centuries, but was more like dogmatic doubt than the modern version. Bertrand Russell put their creed as “Nobody knows, and nobody can know”. They may simply have a bad press. Carneades, one-time head of the skeptical academy, was accused of denying the possibility of all knowledge. In fact he seems to have denied the possibility of certain knowledge, a very different thing.

Continue reading

The Noble Pharmacist

NEW AGE theory holds that practically all cultures had a tradition of using medicines (mostly herbal) and that there is a danger that “Western medicine” will replace these, so losing irreplaceable knowledge.

Continue reading

Playing with Fire

AROUND 40 years ago, at Hull Fair in England, I saw a man dip his fingers in molten lead. He also poured it into his palm and ran it through his fingers. He seemed to suffer no harm although it was real lead; I found a solidified splash and checked. In my vacations I used to work for one of the showmen at the fair, so I found my boss. “That fellow with the molten lead, why doesn’t he burn his hands?”

Continue reading