There are no definitive diagnostic tests for CP/CPPS. This is a poorly understood disorder, even though it accounts for 90%-95% of prostatitis diagnoses. It is found in men of any age, with the peak onset in the early 30s. CP/CPPS may be inflammatory (category IIIa) or non-inflammatory (category IIIb). In the inflammatory form, urine, semen, and other fluids from the prostate contain pus cells (dead white blood cells or WBCs), whereas in the non-inflammatory form no pus cells are present. Recent studies have questioned the distinction between categories IIIa and IIIb, since both categories show evidence of inflammation if pus cells are ignored and other more subtle signs of inflammation, like cytokines, are measured. In 2006, Chinese researchers found that men with categories IIIa and IIIb both had significantly and similarly raised levels of anti-inflammatory cytokine TGFß1 and pro-inflammatory cytokine IFN-γ in their expressed prostatic secretions when compared with controls; therefore measurement of these cytokines could be used to diagnose category III prostatitis.