Coombs' test involves taking a blood sample which is checked for the presence of antibodies which may destroy red blood cells.
You can use the HP Print and Scan Doctor to test the status of the printer spooler, print queue, device manager, and device conflicts. 1  On the desktop, double-click the HP Print and Scan Doctor icon to open the tool. 2  Click Start on the Welcome screen. 3  Select your printer, and then click Next.  Click Fix Printing.
Then see the scanning options in this document to complete scans from the computer. 1  Turn on the printer. 2  If your printer is connected to the computer with a USB cable, disconnect the cable from the computer. 3  Go to HP Customer Support - Software and Driver Downloads.