Monthly Archives: April 2016

“Tough Love”

Disease X is diagnosed by using a PCR on a nasopharyngeal swab which has a sensitivity of 90%. However disease X can also be diagnosed by using a throat swab but with a lower sensitivity of 70%.

Do you accept the throat swab for testing?

Many laboratories do…

However by doing so I think we are accepting second best, regardless of how the result is reported, or what disclaimers are added.

By rejecting such a throat swab and asking for a nasopharyngeal swab (or whatever the optimal sample might be), the requestor/s quickly learns what swabs should be taken. It does not take long for the laboratory to start getting the correct samples consistently, and as a consequence, give out the best results.

Regardless of which microbiology discipline you are talking about, when you accept samples that are second best, you can be sure that you will continue to receive them. The difference in sensitivity/specificity is often not appreciated by the requestor, even if it is documented on the report.

Of course you might get a grumpy phone call from an annoyed clinician asking why their patient’s swab was not processed when it was sent to the laboratory, but the ensuing empathy and explanation that is required are all part and parcel of the job. (and water off a duck’s back for me!)

If you want to have a really high quality laboratory, producing really high quality results, then you need to be really strict with what is acceptable for testing…

Tough love.

Michael

“Messy and Clean”

(Apologies for the paucity of posts recently, has been difficult to find the time…)

Processing by the traditional way is a messy business – Not just literally, but metaphorically as well.

Think about it.

Numerous different tests, lots of different agars, enrichment broths and sub-culturing, different incubators, wet films(that is if you believe in them, I don’t), C. difficile testing algorithms (everyone does it different), parasite concentrates and stains, EIAs.

Lots of labour and bench space required, a large skill mix, and truckloads of QC.

The list goes on.

And all for tests, some of which are not actually that sensitive at diagnosing the pathogen…

It is thus no wonder that laboratories are so keen to adopt multiplexed molecular methods for enteric testing. One test, one person, one run, one set of results to interpret. In other words it is clean.

Molecular processing of enteric samples has been difficult for some labs to justify on the grounds of cost. However traditional methods have so many hidden costs associated with them. It is important to dig them all out for the business case.

In the home environment I am not a very tidy person, but I love a clean laboratory…

Michael