Biocompatibility Testing - Needles

A reader asks:

I am new at medical devices biocompatibility. I've been asked to perform a MEM cytotoxicity assay on an arteriovenous fistula needle. I am not really clear on how to perform the extraction of the device; as I've been asked to do it on the final device which has the needle plus the tube. Would it be appropriate to calculate the volume for the extraction based on surface for the tube and weight for the needle, and sum up both volumes, and submerge the device in that volume?

You want to test the fluid pathway of the device and any other part of the device that is inserted into the body, i.e. the route the fluid would take as it enters the body and exterior of the needle.  As you said, in your case it sounds like the area comes from the interior of the tube (and plunger surface), the needle, and some extra for the exterior portion of the needle that is inserted into the body. I would stick to the ISO 10993 standard and just use the surface area calculation, I'm not sure if the standard allows a combination of the weight and surface area calculations.

It sounds like you may be performing the testing yourself, but the easiest way for me to get answers or at least some direction for medical device biocompatibility testing (assuming you end up using them) is to call Nelson Laboratories, NAMSA, Pacific Biolabs, or WuXi Apptec.  If this is your first time getting testing done- call all four (or at least the first two) and see which one you like, if this is not the first time, generally someone in the company has some strong opinions on which one is best. 

Good luck with your testing.

510(k) Approval Timeline Part 2

My original 510(k) approval timeline is my post popular post ever!  I didn't even follow up with my latest project information.  We extended the disposable product line and it was 30 day FDA review, no questions asked / response required, approval in April to May 2010.  We justified not doing sterilization, biocompatibilty, shelf life, and packaging.  All in all it was about as good as it can get time wise.  Timeline went something like this:

• August to December 2009: Concept and prototype to design
• Jan to March 2010: Product build and verification / validation testing
• April to May 2010: 510(k) Approval

Our validation was an animal study using a physician, who filled out a questionnaire like one to ten, how much is this better than the predicate device after he or she used it, oh boy did I learn something there, I'll go over that some other time.

Now we just have to sell them...