The first step in assessing a treatment effect is to look at the background noise. From the evidence of one case should we now adopt the mother's kiss technique as first line treatment for other children with nasal foreign bodies? The mother's kiss technique is a clear example of a rapid effect (seconds) in a stable condition. The size of the effect can be calculated as a relative rate: it takes less than 10 seconds to see the effect of the mother's kiss, compared with the hours beforehand (for 2 hours this is 720 periods of 10 seconds) with no movement of the foreign body. So the rate ratio of removal for a single case is:
Rate ratio=rate of progression during treatment/rate of progression during non-treatment
(Note that we replaced the 0 cure rate with 0.5, a half correction that allows for a rate between 0 and 1, providing a more robust estimate and avoiding division by zero. Note also that an occasional spontaneous cure—for example, from sneezing—would still result in a large rate ratio.)
This relative rate represents a large signal to noise ratio and is also significant (P<0.01) because, under the null hypothesis, the chance that the cure occurred in the treatment period used out of 720 possible periods is 1/720. However, the apparent effect is likely to be an overestimate as we are likely to note and report the successes rather than the failures.8
To generalise, we need data derived from several carefully assembled case series.9
A search yields only one report of a case series, in which the mother's kiss was successful in 15 out of 19 children.4
We think this is sufficient evidence to recommend use in practice without randomised trials. However, it clearly fails sometimes and it would be worth documenting why and doing randomised trials comparing techniques that are unlikely to have greatly different effects.
With stable or progressive conditions, rapid effects of treatment are easy to demonstrate—for example, the effects of removing a cataract on vision or of cholinesterase inhibitors for organophosphate poisoning. Many surgical procedures also fall into this category—for example, drainage of a pleural effusion or pneumothorax, any operation to arrest haemorrhage, repair of a hernia, and incision of a perianal haematoma.
To generalise further, we can try to predict the outcome (current prognosis) without treatment. This can be clear and easy for stable or progressive conditions but can be highly unpredictable in fluctuating or probabilistic conditions. Prognosis can be classified from most to least predictable as:
- Stable—for example, portwine stain, lodged foreign body
- Progressive—for example, otosclerotic deafness, cataract, many cancers
- Spontaneously remitting—for example, colds, viral rashes
- Fluctuating—for example, rheumatoid arthritis, eczema, and depression
- Episodic—for example, migraine, asthma
- Probabilistic (a possible future event)—for example, stroke