You can know for sure with a CXR showing changes to the density of the lung tissues, esp the lower lobes or left lobe in the case of aspiration, elevated WBC is also a good clue, also, the character of the sputum if any may lead you to an idea if it is pnuemonia or CHF. Sputum C&S can be done but is difficult in elderly pts. due to frequent difficulties with cough/deep breathing. Often you must suction for a good sample and this causes increased secretions and can make resps more difficult, I try to aviod this unless MRSA or VRE is suspected. Some Docs also order blood culture. The s/s of pnumonia are often atypical in the elderly but once you see it alot, you can pick up on the differences found on assessment in CHF and pnumonia rather quickly. If further tests are not ordered, the MD is relying totally on your assessment info for the DX or going with her/his best guess. No CXR = No confirmation of pnuemonia. If you are just flying on S/S I would look for cough, fever, purulent sputum first, but, these may all be absent. Next would be change in mental state, chills, chest pain, dyspnea, tachypenia, lethargy and loss of appetite or vomiting. Other conditions may exhibit exacerbation in major infection also, ie- blood glucose goes through the roof. Any or all vital signs may change form base line. It is not uncommon for a resident with a normal temp of 97-98 degrees drop to 95, or have funky B/P and/or pulse.