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  #1  
Old 06-27-2013
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Arrow Explaining once and for all the pertinent negative crap!

Okay, after rummaging my head for last few days, I think I have cracked this behemoth. Thanks to Novobiocin and Xpazex on clarifying these troubling concepts. I will just take it one step further, and you guys are more than welcome to comment on it. This is what I've thrown out from my mind. The main confusion in negatives that I found is:

1-Should we write the negative finding that SUPPORT the diagnosis?
2-Should we write the normal findings we EXPECT TO BE WRONG?

Take a minute to re-read the above 2 points. They are both negatives but are VERY different. So, here goes my explanation in deciphering them.

#1 is actually not a negative. It is, but I like to think of it as more of a positive. It favors your diagnosis. For instance, in a case of Cystits, "ABSENCE OF FEVER" is a positive finding, i.e. temperature was normal. This favors Cystits. If Fever was present, then its a negative finding, and goes against your diagnosis i.e favors Pyelonephritis instead of cystitis.

#2 is a negative that goes against your diagnosis. For instance in Cystits, we expect to have Dysuria. If there was no Dysuria, then "NO DYSURIA" is a negative that goes against your diagnosis. You could instead write "Normal Urination". Therefore

Cystits
Hx findings:
+Frequency
+Nocturia
+Absence of fever
-No Dysuria

P/E
+Absence of CVA
+Abd WNL

This -ve/+ve signs are hard to understand. A simpler way I think is just to mention Absence/No for the diagnosis, and mention the normal findings for the P/E. Eg

Lets take a simple case of Sore throat, Hx of sexual contact and nothing else. In this case:

Strep Throat
Hx Findings:
Sore Throat
Absence of cough

P/E
Temp normal [We expect Fever]
Oropharnyx pharngeal exudates

Mono
Hx findings:
Sore throat
Sexual contact

P/E
No LAD [We expect Lymphadenopathy]
Temp Normal [We expect Fever]
Oropharynx pharngeal exudates
No HSM [We expect HSM but its not there]

So, what do you guys think? Does it clear things out, or confuses them even more? And Novobiocin/Xpazex your input is highly appreciated as usual!

Any comments/criticism is more than appreciated!
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  #2  
Old 06-28-2013
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first of all thanks for the explanation. at first I was also confused about this NEGATIVE and POSITIVE findings but looking at the patient note sample in the usmle web site I see that their note is pretty simple and straightforward. actually in that sample note there are NO NEGATIVE FINDINGS only the positive and relevant ones. so I think we should focus on listing the pertinent positives. they will be more than enough in most of the cases. I mean, I dont wanna sound like the exam is gonna be easy, actually I think that people like us taking this exam in this new format are in certain disadvantage since we dont have any reliable sources or books like first aid to give us accurate information about this new changes, but like I said I think we should try to focus in the positive findings.
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Old 06-28-2013
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Quote:
Originally Posted by Smashingdude View Post

So, what do you guys think? Does it clear things out, or confuses them even more? And Novobiocin/Xpazex your input is highly appreciated as usual!

Any comments/criticism is more than appreciated!
You absolutely right. It is really simple to write the pertinent negative as shown by your examples.
Also, let me be very clear about one thing-on the real test you will not find many positives apart from the chelef complaint and maybe one positive finding on PE. That's why pertinent negatives become very important to fill in all the blanks since it is recommended NOT to leave any spaces blank.
The USMLE website PNs example show the MINIMUM you need to do to pass but that does not cover you for the mistakes you will (invariably) make in your PE part of ICE. Therefore it is very important to write the pertinent negatives to cover for any mistakes in the other parts of ICE to pass comfortably. Otherwise you will be taking a risk.
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  #4  
Old 06-28-2013
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Sorry, just a point of clarification here. You can actually get fever due to cystitis right? I mean fever can be caused by anything that would cause inflammation such as infection. So writing no fever for cystitis can be viewed as not supporting it.
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Old 06-29-2013
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Quote:
Originally Posted by stupidme View Post
Sorry, just a point of clarification here. You can actually get fever due to cystitis right? I mean fever can be caused by anything that would cause inflammation such as infection. So writing no fever for cystitis can be viewed as not supporting it.
Nope...Fever/CVA tenderness are 2 cardinal signs supporting an UPPER urinary tract infection. You get fever because of bacteremia or leukocytosis that happens with Upper urinary infection.

Lower urinary infection, like cystits/urtheritis are LOCAL inflammations. There are no systemic findings in these cases. Fever is a systemic finding, meaning the thermostat in hypothalamus has been changed. This requires bacteremia or leukocytosis - a systemic inflammatory response in other words. That can only happen with an UPPER infection.
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  #6  
Old 06-29-2013
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Isn't fever because of the inflammatory cytokines released by wbcs and other immune cells? So technically, you can get fever with any type of inflammation? And since the urethra/bladder/kidneys all have blood supplies then infection from any of these could cause fever. I thought it was mainly cva tenderness (upper tract involvement) and chills (higher degree of fever) that would make pyelonephritis more likely compared to cystitis. Correct me if I'm wrong but I've always thought that both can present with fever though it is usually higher in pyelonephritis.
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Old 06-29-2013
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Quote:
Originally Posted by stupidme View Post
Isn't fever because of the inflammatory cytokines released by wbcs and other immune cells? So technically, you can get fever with any type of inflammation? And since the urethra/bladder/kidneys all have blood supplies then infection from any of these could cause fever. I thought it was mainly cva tenderness (upper tract involvement) and chills (higher degree of fever) that would make pyelonephritis more likely compared to cystitis. Correct me if I'm wrong but I've always thought that both can present with fever though it is usually higher in pyelonephritis.
Yes, rarely Cystitis may give a low-grade fever. But, its not the most common presentation. In fact, one of the criteria to differentiate Upper from Lower that we used in clinics all the time was presence/absence of Fever/Pain. You can check Kaplan IM notes to confirm this. I think it mentioned low-grade fever rarely.
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Old 06-29-2013
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I guess it's just difference in our institutions. Symptoms we use to distinguish the two include back pain and chills. Fever if high can point to pyelonephritis more but low grade fever is very common, even non-infectious inflammation can cause low grade fever. I would suggest writing absence of high grade fever rather than just fever in the supporting evidence for the differential, but that's just me.
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Old 06-29-2013
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but what if we just give a look on the practice pn on usmle site ,it clearly states right those pertinent + and - findings that SUPPORT each diagnosis,,,,so why should i write any - finding from any where either hx or p/e that infact is pointing away from my d/d ,,,

and one more thing if pt has fever in any case that ll be mentioned in doorway info,and we need to consider that correct.

one more thing kaplan core cases third edition leaves a lot of blank space in section of this + and - findings ,,so i do not think leaving any blank space in d/d p/e section ll matter ,instead of writing that finding that is pointing away from that d/d

SIMPLE ,,,,WRITE ALL THAT IS SUPPORTING YOUR D/D NOT EXCLUDING IT
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Old 06-30-2013
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Quote:
Originally Posted by Novobiocin View Post
Lolzzzz....I feel you man..!
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Old 07-01-2013
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Quote:
Originally Posted by Smashingdude View Post
Okay, after rummaging my head for last few days, I think I have cracked this behemoth. Thanks to Novobiocin and Xpazex on clarifying these troubling concepts. I will just take it one step further, and you guys are more than welcome to comment on it. This is what I've thrown out from my mind. The main confusion in negatives that I found is:

1-Should we write the negative finding that SUPPORT the diagnosis?
2-Should we write the normal findings we EXPECT TO BE WRONG?

Take a minute to re-read the above 2 points. They are both negatives but are VERY different. So, here goes my explanation in deciphering them.

#1 is actually not a negative. It is, but I like to think of it as more of a positive. It favors your diagnosis. For instance, in a case of Cystits, "ABSENCE OF FEVER" is a positive finding, i.e. temperature was normal. This favors Cystits. If Fever was present, then its a negative finding, and goes against your diagnosis i.e favors Pyelonephritis instead of cystitis.

#2 is a negative that goes against your diagnosis. For instance in Cystits, we expect to have Dysuria. If there was no Dysuria, then "NO DYSURIA" is a negative that goes against your diagnosis. You could instead write "Normal Urination". Therefore

Cystits
Hx findings:
+Frequency
+Nocturia
+Absence of fever
-No Dysuria

P/E
+Absence of CVA
+Abd WNL

This -ve/+ve signs are hard to understand. A simpler way I think is just to mention Absence/No for the diagnosis, and mention the normal findings for the P/E. Eg

Lets take a simple case of Sore throat, Hx of sexual contact and nothing else. In this case:

Strep Throat
Hx Findings:
Sore Throat
Absence of cough

P/E
Temp normal [We expect Fever]
Oropharnyx pharngeal exudates

Mono
Hx findings:
Sore throat
Sexual contact

P/E
No LAD [We expect Lymphadenopathy]
Temp Normal [We expect Fever]
Oropharynx pharngeal exudates
No HSM [We expect HSM but its not there]

So, what do you guys think? Does it clear things out, or confuses them even more? And Novobiocin/Xpazex your input is highly appreciated as usual!

Any comments/criticism is more than appreciated!
This is a perfect way to put it, you are absolutely right on everything you posted, follow this simple rule you devised and you will be all right!

It is no confusing at all, in fact if somebody would've posted this when I was studying for my exam my life would've so much easier!
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Old 03-05-2014
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The CS guide from the website says:

Quote:
You should also indicate the pertinent positive and negative findings obtained from the history and physical examination to support each potential diagnosis. - pg 8 (emphasis mine)
This means that everything you put under a diagnosis must support that diagnosis, not refute it.

I think it's logical to assume that what the guide meant by "positive findings" are simply those that are present, and by "negative findings" they simply mean those that are absent.

Negative or absent findings can support a diagnosis. The absence of crackles in a patient with cough favors an URTI over a pneumonia, for example. The absence of cough in a patient with sore throat supports the diagnosis of strep pharyngitis. These are most probably the "negative findings" they are looking for.
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Old 03-05-2014
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Dont bother much over it Dr Pepper. I gave the exam, and my verdict on these pertinent negatives is that you can do the exam even without them, perfectly, with high scores!

I mentioned the negatives only in the P&E section of the exam only, and rarely only in a few instances, in the supporting rows for the individual diagnosis. But mostly, I put all the negatives in the P&E section, even those that werent related to the case.

Verdict: You can only put the negatives in P&E, and you will be fine. No need to write them out in the supporting diagnosis rows for P&E

Hope that helps everyone, and lays to rest this CRAP!
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Old 03-15-2014
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Yeah Dr. Pepper is right. You were also right in the first half of your original post Smashing where you used the negative finding of 'no fever' to support your Dx of cystitis, therefore making it a PERTINENT negative.

By the way what do you mean you used pertinent negatives only for P/E but not the DD??? Why wouldn't you???

For example of you find no CVA tenderness, and you right that for the P/E part of the PN, why not use that as a P/E finding for the differential to support cystitis??

Please clarify that. Thanks.
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Old 03-17-2014
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Quote:
Originally Posted by Dr_Swagg View Post
Yeah Dr. Pepper is right. You were also right in the first half of your original post Smashing where you used the negative finding of 'no fever' to support your Dx of cystitis, therefore making it a PERTINENT negative.

By the way what do you mean you used pertinent negatives only for P/E but not the DD??? Why wouldn't you???

For example of you find no CVA tenderness, and you right that for the P/E part of the PN, why not use that as a P/E finding for the differential to support cystitis??

Please clarify that. Thanks.
As I said, its too confusing of what negative to use. Its better to avoid it altogether, and just mention the negatives in the P/E section. And frankly, you wont have time to come up with the negatives in the supporting rows of diagnosis. I tried to put a few, but not much. And its absolutely fine! Trust me!
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Old 03-22-2014
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Quote:
Originally Posted by Smashingdude View Post
As I said, its too confusing of what negative to use. Its better to avoid it altogether, and just mention the negatives in the P/E section. And frankly, you wont have time to come up with the negatives in the supporting rows of diagnosis. I tried to put a few, but not much. And its absolutely fine! Trust me!
Thanks.

What about in the differentials, what if it's clear that its a certain diagnosis. For the second and/or third differential you won't have much findings for them right? Also I assume you can just use the same findings multiple times (for each differential) if need be??

Lastly, for the P/E I believe you wrote that you put down tests that you actually didn't do? For example, negative Murphy sign even if you didn't do it? Or am I wrong? Or did you do them and just write them even if they had nothing to do with the case?
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