This blog is usually concerned with covering the latest developments – but this post features a paper published in 1962! Have you ever wondered what would happen if you didn’t do hand hygiene? Well, this remarkable, shocking, and absolutely unrepeatable study from the 1960s gives us the answer: the result would be transmission of pathogens that can cause HCAI.
The cohort intervention study was performed in a nursey for newborn babies in the US (I hesitated to say neonatal unit, because they weren’t really invented then!). The study comes with a health warning for the modern reader: the methods and study design are shocking, and wouldn’t make it anywhere near a modern ethics committee! The study was performed in a 7 bedded nursery for newborn babies. Babies with the same strain of S. aureus were placed in the index cot, and the other six cots arranged in two rows of three, designated rows A and B. The nursing staff on the unit were required to handle the index baby before any of the other babies. Then, nurses allocated to the A cots performed hand hygiene, whereas nurses allocated to the B cots did not perform hand hygiene.
Over the 48 days of the study, 16 different index babies were used. 92% of the 49 babies admitted to the B cots (without hand hygiene) acquired the index strain, compared with 53% of the 32 babies admitted to the A cots (with hand hygiene) (see Figure). Since this study was performed in a largely pre-stats era, I’ve run a Fisher’s exact test, and this difference is statistically significant (p<0.001).
Figure: Graphical representation of the acquisition of S. aureus in a neonatal setting, with and without hand hygiene.
The study also showed that the average time to acquisition was considerably shorter for babies in the B cots (without hand hygiene) at 35 hours compared with 133 hours for the babies in the A cots (with hand hygiene). I think a survival analysis would be the best was to compare these figures, but I can’t do that without access to the raw data (this study was also in the pre data-sharing statement policy era…!).
This study raises all sorts of questions and reflections:
- It’s difficult to understand why the study was allowed to proceed. Since the days of Semmelweis (which was a long time before 1962…) we have known that hand hygiene prevents the transmission of pathogens in the healthcare setting. And there is no mention of consent by the way.
- It is reassuring to see that ‘no clinical staphylococcal disease other than the occasional mild impetigo’ was observed. To see the rate of impetigo would be fascinating. And I bet they didn’t track any differences in outcomes over a longer period!
- You could try to make the case that “It’s only antibiotic susceptible aureus, and about 1/3 of humans carry that anyway.” Except that a) these are newborn babies, working out their microbiota and b) colonisation with S. aureus is a risk factor for infection.
- Why did around half of the babies in the A cots (with hand hygiene) acquire the index strain? Well, we don’t know anything about compliance with the intervention – how many of the nurses caring for the A babies actually washed their hands? 100%? I doubt it. Or perhaps the hand hygiene step was only partially effective (it was a 10 second waft with some disinfecting solution). (Incidentally, the disinfectant used, hexachlorophene, was banned several years after the study due to its toxicity and side effects…) Or perhaps, since only the nursing staff were allocated to hand hygiene or not, other staff groups (like doctors…) explain the high transmission rate in the A cots?
- What was the role of intermittent carriage or staff colonisation in the transmission dynamics in this study?
This study probably shouldn’t have been done in the first place, and we certainly won’t see anything like it performed again. However, it does graphically and dramatically illustrate the importance of hand hygiene to maximise patient safety.