A Challenge to Cloth Theatre Caps?

In recent months the “Theatre Cap Challenge” has been picking up steam on Twitter & has had significant coverage on mainstream media as well. In case you’re wondering what all the fuss is about, you can check out my video in this post or check out the twitter feed below.

While it’s been great seeing this initiative gain momentum, it seems that a significant number of people are hitting a hurdle in adopting it because their hospital doesn’t allow reusable cloth caps citing infection control concerns. In Australia, the ACORN standard is usually cited as the reason for not allowing them, though not all hospitals are interpreting the standard in the same way, and the standard itself allows individual hospitals to develop their own policy on cloth caps.

Given this “challenge to the challenge”, I thought I’d dig a bit deeper and see what the ACORN standard actually had to say on this issue and even go right back to the references cited by ACORN to see if they supported  the recommendations contained within their standard. It’s not my intention to impugn the authors of the document, as I know how difficult and time consuming it can be to research and develop these sorts of documents. Indeed, as I’ve compiled this blog post, I’m sure there’s things I’ve missed, parts of the standard I’ve misunderstood, or references I’ve misinterpreted. And as already mentioned, the authors have left it up to individual hospitals to develop their own policies that are relevant to their local conditions, so any problems being faced may be due more to local interpretation of the standard, rather than the standard itself.

Now, before I discuss my findings, I also want to say that I whole heartedly agree that surgical site infections (SSIs) are nasty and expensive, and infection control policies are important in trying to minimise them. However it’s because of this importance that we need to make sure the policies are evidence based so our efforts are directed towards interventions that actually make a difference. Otherwise the effective policies get lost in the noise of ineffective policies, and precious time and money is wasted implementing and enforcing these policies that don’t work. Front line staff are then tempted to throw the infection control baby out with the bad policy bathwater. We also need to be aware that no policy is an island, and that implementing any policy, good or bad, may result in goal conflicts and unintended consequences.

So, with the background out of the way, onto my findings. I thought I’d start with a TL;DR summary with a take home message and some key points for those that are time poor, before looking at the policy in more detail (it’s quite long sorry, I wanted to be thorough!).  To be clear, I am only addressing “Standard Statement 2” of Perioperative Attire in the 14th edition of the ACORN Standard .

Take home message Despite limited evidence from studies utilising patient-centred outcomes, theatre staff should wear a head cover as part of a strategy to reduce surgical site infections. Any marginal gain from mandating disposable head covers over cloth ones is unwarranted on current evidence as provided in the ACORN Standard, and any clinical difference is unlikely to be detectable using current methods. Surface contamination and SSIs are far more likely to be influenced by factors other than the fabric used in the manufacture of theatre staff head covers. Staff choosing to wear cloth caps should give consideration to how they will launder them, and the need to replace them at appropriate intervals.

Key Points

  1. The evidence for theatre staff wearing head covers, of any kind, is relatively weak, even less so if trying to discriminate between different types of head covers. Many of the cited theatre based studies are decades old, and complicating factors include type of theatre ventilation (conventional vs laminar), scrubbed vs un-scrubbed staff, and underspecification of the type of head cover used in the study. None of the studies directly compared disposable vs cloth caps. On the whole I believe wearing a head cover is entirely reasonable but mandating a disposable cap over a cloth cap is unsupported by these studies.
  2. Many of the studies utilised surrogate endpoints such as air sampling, surface contamination and colony forming units (CFU) on “settle plates” rather than surgical site infections themselves. While this is understandable, it means caution is needed when extrapolating these data to patient-centred outcomes.
  3. Often, data from studies looking at scrubs and surgical gowns is extrapolated to include recommendations about head covers. I’m not convinced this extrapolation is valid.
  4. Some studies used to support head covers involved interventions where use of head covers was only one component of a multi-pronged strategy to reduce SSIs, so it is difficult to say what role, if any, the head covers played.
  5. Some of the official standards and legislation quoted don’t apply to head covers.

ACORN Criteria

So, now onto the specific criteria. Here I will quote a line from the standard, with the supporting citations, and below each quote, I will make some comments about each reference. Please note, that as I am only looking at one section of the standard, the citation numbers here differ to those in the full version of the standard.

Standard Statement 2

The scalp, sideburns, facial hair, ears and nape of the neck are completely covered by a surgical head cover to minimise microbial dispersal .

Reference 2: ANZCA PS28 on Infection Control “Hair should be completely covered with a disposable theatre cap or a freshly laundered lint free hat.” ANZCA have recently released another document encouraging use of reusable caps.

Reference 3: 1979 study; “contamination [of the instrument table and wound orifice] can be lowered with the use of an impermeable hood and a large mask covering the entire face except for the areas about the eyes”. Doesn’t elaborate on what this “impermeable hood” is, nor what it was made of. No statistical analysis of the data.

Reference 4: 2006 study; reduction in contamination and SSIs following an intervention that included changing to laminar flow ventilation and behavioural modifications which included, amongst many others, that staff have “no hair visible”. No mention of specific nature of head covers. Brief reference to enforcing behavioural changes but didn’t give specifics of compliance rates etc.

Reference 5: 2004 study; unacceptably high air-borne bacteria counts “despite scrub staff wearing standard occlusive gowns, hats and masks”. Took swabs from foreheads, eyebrows and ears of scrub staff. Found higher growth counts from ear swabs than other sites. Recommended exhaust helmets for arthroplasty and coverage of ears by scrub staff. However, didn’t look at which sites shed more bacteria or skin squames, just which site had higher growth from a swab. Didn’t confirm that the ears were the source of the high air-borne bacteria counts, or that covering the ears would reduce them. Didn’t discuss pathogenicity of the bacteria isolated.


The face, neck, angle of the jaw and hair yield a higher proportion of transient microorganisms , and higher general bacterial density, than other parts of the body .

Reference 6: 2012 Textbook on hair; I’m wondering if this reference was a misprint, and it was meant to refer to the item below it in the bibliography which was on microbiota of the skin ? However even that reference doesn’t talk about those regions specifically in the context of transient organisms, and I’m uncertain about the significance of the distinction between transient and resident microbes.

Reference 3: 1979 Study; “The degree of bacterial contamination of the skin at the angle of the jaw is high”. Not the focus of the study, no reference provided for this statement, and no statistics done on the data.

Reference 5: 2004 study; see above; swabs of ears had higher CFUs than swabs from foreheads and eyebrows. Not compared to other parts of the body.

In addition, the hair, scalp, ears and forehead have been shown to harbour pathogenic organisms .

Reference 3: 1979 review article; see above; this article doesn’t mention hair, scalp, ears and forehead, only the angle of the jaw without going into more detail. Furthermore it didn’t specify what organisms were grown, whether they were pathogenic or not (isn’t any organism potentially pathogenic?), nor which part of the body they came from, just that the number of CFUs from the instrument table and wound orifice were higher when staff didn’t wear an “impermeable hood and a large mask covering the entire face except for the areas about the eyes” compared to when they did. No statistical analysis of the data.

Reference 5: 2004 study; see above; swabs from ears and forehead grew bacteria but no discussion of their pathogenicity. Mostly coagulase-negative staph and the occasional S. Aureus. No mention of hair or scalp.

Appropriate, well-fitting surgical head covers confine hair, skin squamae and microorganisms that may be shed from these areas and several studies conclude that the use of head and hair coverings reduce contamination of the operative site and the sterile field .

Reference 8: 1998 review article; makes the statement that “in a vertical laminar-flow enclosure both hats and masks are an important part of theatre dress.” without discussing the types of hats and whether they were “well-fitting” or not. The article this review references is a study from 1996 involving sham operations and the use of settle plates and air-sampling. They found hats, masks and clothing made no difference to the CFUs in conventionally ventilated theatres, and while the absence of a hat increased CFUs in laminar flow  theatres, air-sampling was still below the threshold for “ultraclean air”. They referred to 2 types of hats, Surgine and Fabric 450. I gather Surgine is a brand name, and Fabric 450 refers to a type of fibre mix? No difference was found between the two types of hat.

Reference 3: 1979 review article; see above; head cover tested was “an impermeable hood and a large mask covering the entire face except for the areas about the eyes”. No statistical analysis of the data.

Reference 4: 2006 study: see above; “no hair visible” was one feature amongst many of a “behavioural intervention”. No description of head covers used.

Reference 5: 2004 study; see above; didn’t look at contamination of surfaces, only cultures grown from skin swabs of staff; they suggest covering ears, but didn’t provide data or references to show this intervention would be effective at preventing shedding/contamination.

Reference 9: 2008 “Letter to the Editor”; I think this might be a typo or mis-reference? It has nothing to do with head covers or surface contamination. It is a letter reporting data about microbes grown from staff lanyards.

Reference 10: 1988 review; actually showed head covers made no difference! They looked at “all manner of head covers…and found that short hair, long hair, using head covers or investing hoods, or using no head covers at all made no significant difference.”

Reference 11: 2006 case series of SSIs traced back to a particular surgeon; surgeon had been wearing a cap during the cases; changing to a “hood-style cap” was part of a raft of measures introduced to stop the outbreak. Authors suggested most likely source was eyebrow dandruff.

Reference 12: 2004 review; suggested “there is little evidence to suggest that the wearing of surgical face-masks or caps by non-scrubbed theatre staff reduces SSI rates” in conventional airflow theatres, but some reduction in contamination if operating team wore head covers.


(NB: there are other criteria that didn’t provide a reference or were unrelated to the question of cloth vs disposable caps)

Personnel have a duty to: 2.1 apply a head cover that encloses all hair, including sideburns and facial hair, and covers the nape of the neck .

Reference 4: 2006 study; see above; a wide-ranging behavioural intervention, of which “no hair visible” was one small part, showed a reduction in SSIs; didn’t specify type of head covers, or compliance rate

2.2 ensure the forehead and ears are covered by the surgical head wear .

Reference 3: 1979 review article; reduction in CFU count with “the use of an impermeable hood and a large mask covering the entire face except for the areas about the eyes”. No description of the hood, and no statistical analysis of the data.

Reference 5: 2004 study; see above; only showed bacteria present at these sites in some, but not all, staff. Didn’t test if covering them reduced shedding, contamination or SSIs.

2.6 demonstrate that cloth head covers meet the relevant Australian Standards for perioperative attire textiles, labelling, and laundering .

Reference 8: 1998 review article; see above; no mention of the Australian or ISO standard, and no reference to textiles, labelling or laundering and only a brief mention of head covers being “important”.

Reference 14: 2003 ISO standard on Medical Devices and regulatory requirements for quality management systems. I haven’t been able to view the full document, but I wonder if this may be another mis-reference? Perhaps they consider a head cover a medical device?

Reference 15: 1999 review article; no mention of Australian standards, labelling or laundering, and actually suggests head covers make no difference; “The use of head covers and masks did not significantly lower the contamination.” Some discussion of cloth vs paper vs plastic gowns, but no mention of textiles in the discussion of caps.

Note: Fabrics composed of 100% cotton must not be used for cloth hats. It has been known for some time that regular cotton provides an ineffective barrier to skin squamae .

Reference 16: 1990 study comparing different combinations of cotton or synthetic scrubs, and cotton-exhaust operating gowns or synthetic gowns, and their effect on air-sampling and CFUs. All air-sampling had low CFU counts, but cotton scrubs + synthetic gowns were higher than synthetic scrubs with synthetic gowns. Best performance was with cotton scrubs and cotton exhaust gowns. I have not seen any hospital that uses the synthetic scrubs (Gore-Tex and Selguard) used in this study. There were significant differences between the different scrubs aside from the fabric type so it’s hard to tell if the differences was due to the fabric or some other design feature.

Reference 17: 2002 study comparing CFU counts from air-sampling during crossover study of staff moving from cloth scrubs to occlusive synthetic scrubs. Surgical gowns were the same throughout the study period. Showed a significant reduction in CFU counts with the occlusive scrubs however as with reference 16, the fabric was not the only difference between the scrubs worn in different study arms, so it is difficult to draw strong conclusions regarding fabric choice from these two studies alone.

2.11 Woven fabric hats must:

2.11.1 be constructed of fabrics and by methods which meet the specifications in the relevant Australian Standard AS 3789.3:199414 .

Reference 18: This Standard doesn’t include head covers, only dresses, shirts, pants, jackets and shoe covers.

2.13 be tracked in use and laundering, because the number of launderings decreases barrier effectiveness of woven fabrics .

Reference 19: 1998 study looking at the effect of laundering on bacterial transmission through surgical gowns. Not surprisingly laundering does degrade the performance of the fabric but not sure how relevant this is for caps as opposed to surgical gowns?  Also, I am not sure of the validity of the testing procedure which measured the transmission of bacteria though the fabric under hydrostatic pressure which seems unlikely in everyday use, especially for a head cover. It would seem that others also share this concern . Furthermore, I’d be  interested to know if hospitals would be able to provide  the number of laundering cycles any given item of hospital provided clothing had undergone?

Note: A mandatory standard (AS/NZS 1957:1998) exists for care labelling and applies to anyone supplying clothing and textiles . Failure to comply with this mandatory standard is an offence under the Competition and Consumer Act 2010 (Cth) and may result in fines of up to $1.1 million if the person is a body corporate and $220 000 if the person is not a body corporate.

Reference 21: I’m not exactly sure how they came to that conclusion but I suspect it has to do with Contravention of Industry Codes as described in Sections 51ACAff of Part IVB of the Competition and Consumer Act 2010. However, the Australian Standard referred to above is actually voluntary, and the  Consumer Protection Notice No.25 of 2010 of the Trade Practices Act 1974 then uses certain sections of that standard as a basis for mandatory requirements for the labelling of a variety of prescribed products as described here. This notice explicitly exempts head wear  from the Care Labelling Requirements of Australian/New Zealand Standard AS/NZS 1957:1998 so the labelling standard doesn’t apply to cloth theatre caps.

Well, that’s it! Thanks for taking the time to read and consider my thoughts on the Theatre Cap Challenge and it’s interplay with the ACORN Standards. I hope you can now appreciate some of my concerns about using the standard as a blunt tool to prevent staff wearing cloth theatre caps. There are advantages to using cloth caps which need to be weighed against any potential disadvantages, including environmental concerns regarding use of disposables, better readability of the name and role, and hospitals will save money if they have to purchase fewer disposable caps. I also think cloth caps look better, and allow staff to express some personality and individuality, which patients seem to appreciate. I hope you’ll get on board and support the Theatre Cap Challenge in what ever form you can, and please don’t hesitate to contact me with feedback, or to point out any errors or misunderstandings on my part.

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