Reddit reviews Symptom to Diagnosis: An Evidence Based Guide, Second Edition (LANGE Clinical Medicine)

Check out this book to help fine-tune approaching different chief complaints:

"From Symptom to Diagnosis"

http://www.amazon.com/Symptom-Diagnosis-Evidence-Clinical-Medicine/dp/0071496130/ref=sr_1_1?ie=UTF8&qid=1382288255&sr=8-1&keywords=from+symptom+to+diagnosis

Other than that, keep in mind that a differential diagnosis does NOT mean every single possible thing that can cause those symptoms in the patient. You should really focus on 4 or 5 things it could be, based on the chief complaint and initial HPI, and ask questions to narrow down that list even further. That's one of the biggest mistakes I see my classmates doing -- when asked about what their assessment is, they'll give an insanely long list of unlikely things and what questions/physical exam maneuvers they did to rule them out.

Your right about one thing, labs and imaging aren't perfect. But there are statistics that allow us to compare labs/imaging with physical exam maneuvers, they are called likelihood ratios, and depend on the sensitivity and specificity of the particular test (physical exam, labs, imaging, combination, etc).

Let's take PNA, since you imply that your physical exam is able to accurately confirm or exclude PNA as the diagnosis. Here is a paper from 1999 (when common chest Xray was both more expensive and less accurate at detecting PNA than it is now):

https://www.ncbi.nlm.nih.gov/pubmed/10335685

I'll paste the last line of the conclusion for those not wanting to click on the link - The traditional chest physical examination is not sufficiently accurate on its own to confirm or exclude the diagnosis of pneumonia.

Here is another nice write up about it from the University of Washington:

https://depts.washington.edu/physdx/pulmonary/evid1.html

Again, conclusions linked for those not wanting to click link:

Conclusions

Physician agreement about the presence or absence of pneumonia in patients with respiratory illness is relatively low.
No single symptom, historical feature nor physical examination finding is highly accurate in predicting pneumonia.
Prediction rules using combinations of findings are helpful in ruling out pneumonia but chest x-ray is required to accurately diagnose pneumonia.
A screening pulmonary physical examination may include percussion and auscultation for crackles. If abnormalities are detected or if pneumonia is strongly suspected, one may consider maneuvers such as egophony.

I think I've made my point but there's plenty more where that came from. CXR is required to rule in or out PNA, and no physical exam findings (or lack thereof) will change that. If you are using your physical exam findings to decide whether to treat patients or not, bottom line is you're treating patients who don't have PNA or your not treating patients who do, or both.

As for volume status, let me link this nice review:

http://onlinelibrary.wiley.com/doi/10.1111/j.1751-7133.2010.00166.x/full

I'll link a section here for brevity:

In one analysis of adults, dry axilla–supported hypovolemia (positive likelihood ratio, 2.8; 95% confidence interval [CI], 1.4–5.4), while moist mucous membranes and a tongue without furrows argued against it (negative likelihood ratio, 0.3; 95% CI, 0.1–0.6 for both findings).23 In the same analysis,23 capillary refill time and poor skin turgor had no diagnostic value, a finding supported by others. Finally, in a prospective study of blood donors giving 450 mL of blood,24 mean capillary refill time decreased from 1.4 to 1.1 seconds and had a sensitivity of 6% for blood loss. The authors concluded that the accuracy of capillary refill in a patient with a 50% prior probability of hypovolemia was only 64%.

Skin turgor (what you call skin tenting and claim has value) has NO DIAGNOSTIC VALUE according to this study and many others.

If you don't understand + and - likelihood ratios, I suggest reading Symptom to Diagnosis by Scott Stern et al, (https://www.amazon.com/Symptom-Diagnosis-Evidence-Clinical-Medicine/dp/0071496130). It details the evidence behind physical exam maneuvers and shows when its useful and more importantly when its not.