Monthly Archives: August 2013

“Before you even open the door…”

The Science of Microbiology,

AHRENS~1

When a microbiology sample arrives at the lab, then in order for it to get in through the front door, I expect it to be:

  • Not leaking: The leaky sample is not only a potential infectious hazard to those handling it, it also implies that the sample itself is potentially contaminated.
  • Properly labelled: The unlabelled sample is deceptively common (in my experience about 1-2% of all samples). The mismatched labelling of the request form and sample also occurs not uncommonly.
  • In a proper container: I have seen stool samples arrive into the laboratory in Chinese Takeaway cartons and 35mm film cannisters, and get processed….
  • Recently taken: Samples that take too long to get to the lab, for whatever reason, need to be discarded. Again I have seen samples “get lost in the post” for weeks, yet still get processed on arrival…

 

To keep things simple the general rule should be to reject such samples. Processing them is not only a medico-legal risk to the laboratory, it also presents a potential risk to the patient. Processing such samples also just perpetuates the problem. 

The general rule should be to reject, occasionally such samples fall into the “irreplaceable” or “difficult to replace” category, i.e. CSF, theatre samples. The clinical microbiologist should be informed, who then needs to make a clinical assessment as to the importance of processing.

How do you notify the requestor of a rejected sample? This depends on the importance of the sample: A rejected urine or wound swab etc etc I believe should be notified through the normal resulting channels. More critical samples that are rejected such as blood cultures, and other sterile site samples warrant a phone call.

Unfortunately there are still too many specimens getting into the microbiology laboratory that should never even make it past the front door. The laboratory must be the gatekeeper for what samples it deems acceptable and which ones it doesn’t. It seems tough but it is only because traditionally we have been too lenient in the past and just accepted whatever is thrown at us. I regard good rejection criteria documented in the (paperless) manuals as a key quality marker of any clinical microbiology laboratory…

Michael

“A test that is just a bit too good…”

The Science of Microbiology, , ,

On one of my rare forays through a research journal I surprised myself by finding a paper that interested me….

Clinical relevance of a positive molecular test in the diagnosis of Clostridium difficile infection. Baker I et al, Journal of Hospital Infection 84 (2013),311-315. Click here for a link to the abstract. Unfortunately the full text requires subscription.

 

Photo accredited to Dr Holdeman
Photo accredited to Dr Holdeman

 

It has long been thought that toxin assays for Clostridium difficile lack sensitivity. This has triggered a move towards PCR or other molecular testing for toxin producing Clostridium difficile strains.

This paper primarily looks at the clinical differences between patient cohorts who are PCR +ve and toxin EIA negative for C.difficile, and patients who are both PCR and toxin EIA positive.

The study showed increased mortality and prolonged duration of diarrhoea in the toxin EIA positive group, compared with the group that was PCR positive but toxin EIA negative. There was no obvious attributable mortality to Clostridium difficile in the group that was PCR positive but toxin EIA negative. (However this seemed to be only on examination of the death certificates as opposed to detailed review of the clinical notes)

The study shows nicely that by using a molecular test such as PCR for C. difficile detection, it may just be a little too good at detecting it, and thus produce positive results that are not clinically relevant (?mostly just colonising). However the study did not specify whether there was any clinical cases suggestive of severe CDAD in the PCR positive, toxin EIA negative group, which would have been nice to know before discounting this cohort altogether.

These findings confirm my clinical suspicions that we have moved to a test which is just a little too good, and that there is probably a continuing need/role for toxin EIA testing in diagnostic algorhythms for disease due to Clostridium difficile.

The only downside of the paper was the declaration of a conflict of interest by one of the authors, although it looks to be fairly minor.

Nice paper. Worth getting hold of and discussing further in your laboratory journal clubs etc.

Michael

p.s. Click here for a previous article on faecal transplantation to treat disease due to Clostridium difficile.

“Do Cinical Microbiology Laboratories need their own Websites?”

Confessions of a Microbiologist,

In my personal opinion, yes, undoubtedly. Any laboratory that has users outwith its institution should have a public website. And because I define laboratory users as comprising both the test requestors and the patients, this means that virtually every laboratory has users outwith the confines of its parent institution.

Why do clinical microbiology laboratories need websites?

I think microbiology laboratories (and all laboratories for that matter) need a website for three key reasons:

  • Communication: Letting users know about changes in laboratory protocol, new tests, latest information on outbreaks etc.
  • Information: e.g. Current key staff members, operating hours, collection centres, test lists including which tests are sent away, sample collection protocols
  • As a portal for users to contact the laboratory and to feedback any comments about the laboratory service.

Obviously clinical microbiology can be a sub-section of a larger laboratory website which covers all the disciplines.

Websites are so ridiculously easy to set up and maintain these days that anyone can do it (I am living proof of this….), so all clinical microbiology laboratories should at least be thinking about it.

The other key message here is that it is not enough just to set it up and leave it. This is what I call a static website. Websites that are updated from time to time with new information makes it more interesting to the viewer and helps to build relationships up between the laboratory and its users.

Michael