Analysis of effusions

RE: Analysis of effusions

Beats — Thu, 16 Mar 2017 20:34:56 GMT

What is your biochem machine? I use the TotalProtein (as opposed to urine-protein) slides with Idexx VetTest and have found the results to correlate moderately well with external lab reports. I have also found the results to correlate often well with refractometer. Your hematology machine may well do a reasonable total nucleated cell count on the fluid for you as well - I've found the Idexx Lasercyte to give a reasonable estimation of total nucleated cell count.

I don't think a urine dipstick protein pad will be at all useful (I may be wrong on this as I've never used it for this) - it mainly reacts to albumin rather than globulins and is extremely crude.

Re using your refractometer for this, some points to note:

1) Your biochem machine may be more accurate.

2) You are NOT changing the calibration of the refractometer from what you normally do with urine (i.e. still calibrated to SG=1.000 with pure water).

3) You are simply measuring the refractivity of the fluid - as long as you have a scale for this (or any proxy that can be related back to this), you can make a reference chart to relate this to whatever estimation of protein you might consider a pleural fluid of the refractivity might contain (there is a little experimental data on which to base such a scale already out there).

4) You will likely have one of 2 readable scales on the refractometer to save you this effort - either a "total protein" (more likely) or "total solids" (still possible) scale. These are NOT numerically interchangeable it is worth noting! Given that a "total protein" scale might not extend down to refractivities as low as you might find helpful to measure, if you like numbers you might be better measuring off whatever other scales you have on your refractometer and just convert that to a "total protein" scale either accurately or as a ball-park figure or using arbitrary cut-offs.

("Based on the results of this study, the range for reporting body fluid protein concentration by refractometry can be extended down to at least 0.6 g/dL, well below the 2.5-g/dL cutoff level found on many refractometers. Quantitative protein determination could then include most clinical body fluid samples. Standard refractometers limit quantification of protein to ~1.0 g/dL above the published reference ranges for peritoneal fluid from horses6-9 and small animals.1" from VetClinPath 30(1):17

5) The diagnostic utility of knowing the actual protein content of the fluid (let alone an estimation of this), is often pretty low in my experience.

6) Other tests to classify body fluid that are trendy include:

"Based on the results of this study, pleural effusion should
be classified as either a transudate or an exudate using
Light’s criteria which, as previously demonstrated,17 in
our opinion are superior to the traditional veterinary
scheme." Journal of Feline Medicine and Surgery 2016, Vol. 18(8) 666–672

RE: Analysis of effusions

An On MRCVS — Wed, 15 Mar 2017 13:28:45 GMT

Thanks everyone

RE: Analysis of effusions

grumpyoldman — Tue, 14 Mar 2017 22:46:45 GMT

Vet clinics North America Jan 2017, several chapters on pleural, peritoneal, and joint fluid analysis

RE: Analysis of effusions

Anthony Todd — Tue, 14 Mar 2017 17:27:19 GMT

[quote user="Michael Woodhouse"]Refractometer underestimates lower protein concentrations:[/quote]

True but:

CONCLUSIONS AND CLINICAL RELEVANCE:

Results of any of these 4 techniques can be used to rapidly and efficiently differentiate peritoneal and pleural fluid from dogs into transudates and exudates on the basis of total protein concentration less than or greater than 20 g/L, respectively.

from your reference

RE: Analysis of effusions

Sarah Keir — Tue, 14 Mar 2017 17:26:35 GMT

Refractometer helps you estimate total solids in an effusion, not protein content per say. Use the scale on the side opposite from the urine specific gravity (labelled SERUMP) on our refractometer. I don't know the official scale but I say anything >40g/L is high, anything <10g/L is low and anything in the middle is middle so modified transudate!

RE: Analysis of effusions

Michael Woodhouse — Tue, 14 Mar 2017 17:21:14 GMT

Refractometer underestimates lower protein concentrations:

https://www.ncbi.nlm.nih.gov/pubmed/11277189

RE: Analysis of effusions

Anthony Todd — Tue, 14 Mar 2017 17:19:29 GMT

[quote user="An On MRCVS"]This is a dumb question, but.[/quote]

Probably a dumb answer but isn't the SG diagnostic?? Did that all the time with a refractometer....

Another thing you get from an instant chest tap during a consult.

This seems to agree....

http://cal.vet.upenn.edu/projects/sagastro/case7/transudt.htm

RE: Analysis of effusions

Michael Woodhouse — Tue, 14 Mar 2017 16:46:42 GMT

We use urine dipsticks for a rough protein level and cytology (neutrophils and bacteria) generally with diff quick, but do have Gram stain. If milky suspect chyle. If bloody spin it and see if RBCs intact or just hemaglobin, a PCV on the fluid is useful.