t post-revision to his hip replacement. He has a wound infection with bacteremia and methicillin-resistant staphylococcus aureus, but it's questionable whether the infection is related to his surgery. I am planning to list the following codes, but I'm not sure of the order. Also, three of the codes are noted as "Secondary diagnosis use only." Can I only use one of these codes? • 790.7 (Bacteremia); • V09.0 (Infection with microorganisms resistant to penicillins) (SDx); • 041.11 (Staphylococcus aureus); • V58.81 (Fitting and adjustment of vascular catheter); • V58.62 (Long-term [current] use of antibiotics) (SDx); • V54.81 (Aftercare following joint replacement); • V43.64 (Organ or tissue replaced by other means; hip) (SDx). -- Texas Subscriber Answer: "Secondary diagnosis use only" or "SDx" means that the diagnosis has to be coded as secondary. But "secondary" just means that you cannot list the code as primary. Thinking that secondary means second is a common error for coders, but it's not true. Secondary diagnoses can be sequenced anywhere but primary. You would not use V54.81 with this patient because this is not routine care of a joint replacement. Code for infections associated with a prosthetic joint with 996.66 (Infection and inflammatory reaction due to internal joint prosthesis). This code also requires you to code the specified infection, 790.7 for bacteremia and 041.11 for Staphylococcus aureus. To code the resistance (MRSA), use V09.0. Always sequence the V09 codes after the organism code. The 996.66 code also requires you to list a V43.6x code to identify the infected joint. Sequence your other V codes for the fitting and adjustment of the vascular device (V58.81) and (V58.62) for long term antibiotics last. So, your sequencing for this patient would be: • M0230a: 966.66 (Infection and inflammatory reaction due to internal joint prosthesis); • M0240b: 790.7 (Bacteremia); • M0240c: 041.11 (Staphylococcus aureus); • M0240d: V09.0 (Infection with microorganisms resistant to penicillins); • M0240e: V43.64 (Organ or tissue replaced by other means; hip); • M0240f: V58.81 (Fitting and adjustment of vascular catheter); and • Other pertinent diagnoses: V58.62 (Long-term [current] use of antibiotics). Unless otherwise indicated, reader questions were answered by Lisa Selman-Holman, JD, BSN, RN, HCS-D, COS-C, consultant and principal of Selman-Holman & Associates in Denton, TX.