There are many amongst us who are unfortunate enough to be required to read Gram stains as part of our work, and usually lots of them. There will inevitably be occasion when one comes across a stain where it is uncertain whether bacteria are present or not, or whether it is just debris/stain deposit etc. And it usually doesn’t matter how much you look at it! You can scan the slide ad infinitum, then ask your colleague for their opinion, which usually turns out to be identical to yours…. “I’m not sure”

This happens to all of us regardless of our expertise or experience.

The first thing to do of course is to repeat the Gram stain, in the hope that it gives a clearer picture. However if you get a similar picture on repeat testing, how do you report it?

In superficial wound swabs it is of course of minor importance, which makes you wonder why we ever bother doing Gram stains on such samples (we are very selective now in this respect at my laboratory), but occasionally you will come across such a stain in a sterile site sample, such as a CSF or a joint aspirate.

My experience with such results is that when the Gram stain finding is uncertain like this, then it is rarely of help to the clinician, and does little to improve the patient’s outcome. In fact, on occasion, when an uncertain finding of bacteria are reported on Gram stains from joint aspirates, it can occasionally lead to an unnecessary procedure/operation….. I have seen this happen from time to time.

Depending on the level of uncertainty, one could telephone the clinician to relay this uncertainty. “I have had a look at the Gram stain and there might be a few things there which look like Gram positive cocci, but I cannot be certain….” The issue with this however is that uncertainty often becomes certainty by “Chinese Whispers”.

If it is unclear whether bacteria are present on the Gram stain, then depending on the clinical scenario, I think there is a very good argument for not reporting anything at all, as opposed to reporting something which is potentially misleading.

What do you think?

Michael