MDRD or Cockroft-Gault equations re: GFR and NSAID/HTN Meds influence?

My question is - when is the MDRD or Cockrof-Gault equations for estimating GFR more approrpriate?  In regards to a woman, I believe I read somewhere the MDRD when selecting a woman is based on a 150lb gal and not a 230lb gal.  So, how far off is the Cockrof-Gault?

As I had a creatinine level test done (unbeknownst to me that I'd be doing it) about a month ago, when I had taken a lot of NSAIDs (about 6-8 800mg motrins, several aspirins) during that weekend, plus tums, working out with weights, drinking gatorade and had major heartburn and a pulled muscle in my traps.  On top of that, I was taking HCTZ and Methyldopa for HTN - which turns out, I probably haven't needed the BP meds for a long time (7 years worth,) because 30 days later, my bloodpressure is NORMAL.  I also had a big turkey sandwhich the day before the test (again - didn't know I was taking this - so what I could have done wrong, I probably did.)  After getting my creatinine at 1.12 mg/dl my doctor said to stop taking all NSAIDs, and the blood pressure meds to see if my creatinine levels go back to normal as with IDMS, it made my GFR 54.

Can you tell I've SCOURED the web for information?  I've learned more on the web than my doctor has said to me.

Anyway, back to the question - should I believe the Cockroft-Gault which would have my GFR at 111 (115 at the time I took it, but have lost 13 pounds from exercise (moderate walking) and watching sodium and protein intake over the last 4 weeks or should I believe the MDRD?

Also, have seen a few studies that says NSAIDs and HTN meds can influence creatinine between 20-30%.  Is that true?

My brother who was a juvenile diabetic for 25 year, (I am not,) ended up with ESRD and a kidney/pancreas transplant.  But that was due to diabetes.  No one else in my family had kidney problems.

Desperately searching for hope.