Ca(2+) filtered load - USMLE Forums
 USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
 Home USMLE Articles USMLE News USMLE Polls USMLE Books USMLE Apps
 Register FAQs Members List Search Today's Posts Mark Forums Read

 USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam

#1
07-03-2011
 USMLE Forums Guru Steps History: Step 1 Only Posts: 326 Threads: 20 Thanked 220 Times in 124 Posts Reputation: 232

A patient with acute glomerulonephritis has a total plasma Ca2+ of 2.5 mmol/L and a GFR of 160 L/day. What is the estimated daily filtered load of calcium?

(A) 64 mmol/day
(B) 120 mmol/day
(C) 240 mmol/day
(D) 400 mmol/day
(E) 800 mmol/day
 The above post was thanked by: Claus_CU (07-04-2011), curiousmind (08-11-2012), drfchakera (07-06-2011), Mashee (07-04-2011), pnreddy (07-05-2011), prataptetali (07-06-2011), shaan175 (07-25-2012), struggle (07-04-2011), usluipek (07-04-2011)

#2
07-04-2011
 USMLE Forums Guru Steps History: Not yet Posts: 324 Threads: 70 Thanked 239 Times in 144 Posts Reputation: 249

=160x 2.5=400mmol/day
 The above post was thanked by: bebix (07-04-2011), usluipek (07-04-2011)
#3
07-04-2011
 USMLE Forums Addict Steps History: Not yet Posts: 144 Threads: 34 Thanked 33 Times in 24 Posts Reputation: 43
400

This is one of the "come on.. really?" question.
I read this question and instantly the answer was 400. But I was like hmm noo, may be not. Cant be that beginner of a question. Cos the patient has glomerulonephritis so may be the normal equation of FL does not fit here.
RIGHT??

#4
07-04-2011
 USMLE Forums Guru Steps History: Step 1 Only Posts: 326 Threads: 20 Thanked 220 Times in 124 Posts Reputation: 232

Quote:
 Originally Posted by docji This is one of the "come on.. really?" question. I read this question and instantly the answer was 400. But I was like hmm noo, may be not. Cant be that beginner of a question. Cos the patient has glomerulonephritis so may be the normal equation of FL does not fit here. RIGHT??
It is really tricky question, I got it wrong, what why decided to post....
#5
07-04-2011
 USMLE Forums Addict Steps History: Not yet Posts: 144 Threads: 34 Thanked 33 Times in 24 Posts Reputation: 43
?????

Quote:
 Originally Posted by jahn77 It is really tricky question, I got it wrong, what why decided to post....
So whats the answer to this??
#6
07-04-2011
 USMLE Forums Guru Steps History: Step 1 Only Posts: 326 Threads: 20 Thanked 220 Times in 124 Posts Reputation: 232

I was going to wait for more options,

OK, here is the trick, taking into consideration that about 40% of total Ca is bound to proteins and can not be filtered;
The answer will be 240 mmol/day. (60% of 400 mmol/day)

Got the question from Lange Qbank book, physio part...
 The above post was thanked by: awaisnaeem86 (07-05-2011), bebix (07-04-2011), Claus_CU (07-04-2011), curiousmind (08-11-2012), docji (07-04-2011), qurat21 (07-05-2011), rulz (07-06-2011), star123 (07-04-2011), struggle (07-04-2011)
#7
07-04-2011
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,357 Threads: 194 Thanked 3,268 Times in 881 Posts Reputation: 3278

Quote:
 Originally Posted by jahn77 I was going to wait for more options, OK, here is the trick, taking into consideration that about 40% of total Ca is bound to proteins and can not be filtered; The answer will be 240 mmol/day. (60% of 400 mmol/day) Got the question from Lange Qbank book, physio part...
GOOD ONE!!!...
#8
07-04-2011
 USMLE Forums Veteran Steps History: --- Posts: 254 Threads: 21 Thanked 43 Times in 39 Posts Reputation: 53

that is a really good question!
#9
07-05-2011
 USMLE Forums Scout Steps History: Not yet Posts: 27 Threads: 8 Thanked 18 Times in 12 Posts Reputation: 28

The question states Ca2+.......as in free ion, why they would expect you to think that includes non ionic forms bound to protein, is ridiculous and defeats the purpose of a "trick" question. Just a thought.
#10
07-05-2011
 USMLE Forums Guru Steps History: Step 1 Only Posts: 326 Threads: 20 Thanked 220 Times in 124 Posts Reputation: 232

Quote:
 Originally Posted by moe2185 The question states Ca2+.......as in free ion, why they would expect you to think that includes non ionic forms bound to protein, is ridiculous and defeats the purpose of a "trick" question. Just a thought.
I thought same way, but the buzzword - TOTAL plasma Ca2+ which consists of bound Ca and free ionic form.
#11
07-05-2011
 USMLE Forums Scout Steps History: Not yet Posts: 27 Threads: 8 Thanked 18 Times in 12 Posts Reputation: 28

The thing is even with TOTAL being stated it only applies to what comes after that word. If it stated TOTAL serum calcium then sure it would mean ionic and non ionic forms, but if you say TOTAL serum Ca2+ now you are discussing a specific state of calcium.

Nomenclature should be absolute when making questions at this level of education and should not be used as short forms or else it just gets confusing.
 The above post was thanked by: jahn77 (07-05-2011), prataptetali (07-06-2011)
#12
07-05-2011
 USMLE Forums Guru Steps History: Step 1 Only Posts: 326 Threads: 20 Thanked 220 Times in 124 Posts Reputation: 232
Ca2+ - albumin binding

Thank you for good point,I looked back to book, guessing my mistype,but it was written as Ca2+ (ionic form), and than, what RR Biochem says:
"Aspartate and glutamate (acidic): negative charge at pH 7. Albumin has many of these acidic amino acids, which explains why it is a strong binding protein for calcium and other positively charged elements". And Ca2+ binds to albumin as ionic form, not any other type, I guess it is Van der Vaals bonds, what why they easily displaced on change of blood pH.
And wiki says about albumin: Albumin is the main protein of plasma; it binds water, cations (such as Ca2+, Na+ and K+), fatty acids...so it is the same ionic form.
#13
07-20-2011
 USMLE Forums Addict Steps History: Step 1 Only Posts: 122 Threads: 45 Thanked 57 Times in 34 Posts Reputation: 67

Quote:
 Originally Posted by jahn77 A patient with acute glomerulonephritis has a total plasma Ca2+ of 2.5 mmol/L and a GFR of 160 L/day. What is the estimated daily filtered load of calcium? (A) 64 mmol/day (B) 120 mmol/day (C) 240 mmol/day (D) 400 mmol/day (E) 800 mmol/day

Nice question. I ran across a similar one in Kap bank:

Testing of plasma shows plasma Ca2+ as 5 mmol/L and GFR as 150 L/day. What is filtered load for Ca2+:

150 L/day
300
369
550

(I think they missed up the units for the answer choice and should have been mmol / day).

But why it's the answer 40% of the 750 as it was for you problem that you have posted?

One more thing that confused me was that 99% of Ca is bound to bone, 1% in blood and of that 40% is bound, is that correct?

 Tags Physiology-, Renal-, Step-1-Questions

Message:
Options

## Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
User Name:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
 AMG IMG ---
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

 Not yet Step 1 Only CK Only CS Only 1 + CK 1 + CS 1+CK+CS CK+CS 1+CK+CS+3 ---
Favorite USMLE Books
 What USMLE books you really think are useful. Leave blank if you don't want to tell.
Location
 Where you live. Leave blank if you don't want to tell.

## Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.