A diagnostic test apparatus comprises:an elongate housing defining a test strip holder containing a lateral flow test strip；a fluid sampling chamber provided with an opening connecting the fluid sampling chamber with the test strip holder；a viewing window in the elongate housing allowing reading of one or more portions of the lateral flow test strip； anda connector configured to couple the diagnostic test apparatus to a bulk source of fluid.The apparatus may be included in a kit of parts. The apparatus is useful for detecting peritonitis. The bulk source of fluid may be peritoneal dialysate. Various markers may be determined in the bulk source of fluid such as MMP8, IL-6, HNE, MMP2, MMP9, TIMP1, TIMP2, NGAL, A1AT, desmosine, fibrinogen, IL-8, calprotectin, fMLP, IL1b, cystatin C, HSA, RBP4, SPD, MPO, sICAM and TNFa. Detection of the markers to indicate peritonitis may also inform treatment choices.
