An eGFR blood test is used whenever there is suspicion of a kidney disease. This is usually the case in patients who are suffering from diabetes or from hypertension for a prolonged period of time.
In the case that your APP file doesn't open, it is highly likely that you do not have the correct software application installed on your PC to view or edit APP file extensions. If your PC opens the APP file, but it's the wrong application, you'll need to change your Windows registry file association settings. In other words, Windows is associating APP file extensions with the wrong software program.
From EZ Freeware: Open different file types on your computer. Open Microsoft Office documents, Adobe PDF Files, and many other image, movie, and music file types. No specialty software is required to open any of these file formats. With Free Opener, once you download the software, you no longer have to worry about opening files again.