AB0872 Diagnostic efficiency of determining the purine metabolism enzymes activity in the differentiation of gout

Abstract

BackgroundSerum uric acid (UA) level is the most important risk factor for gout. At the same time many people with hyperuricemia do not suffer from gout, and UA level can return to normal during gout exacerbation.Objectivesto improve the diagnostics of the gout.Methods53 gout patients were the target group. The mixed control group was consisted of 150 rheumatoid arthritis patients, 95 osteoarthritis patients, 55 ankylosing spondylitis patients. The diseases were diagnosed in accordance with the international standards. Adenine deaminase, Adenosine deaminase (ADA), AMP-deaminase (AMPDA), Guanine deaminase, Guanosine deaminase, Guanosine phosphorylase, 5'-nucleotidase, Xanthin dehydrogenase (XDG), Xanthin Oxidase, Purine nucleoside phosphorylase activities were determined in blood serum with subsequent evaluation of sensitivity (Se), specificity (Sp), likelihood ratio of positive (LRP) and, likelihood ratio of negative (LRN) result, predictive value of positive and negative results.ResultsThe AMFDA and ADA activities were defined as a screening marker to diagnose of the gout from a joint syndrome another genesis. Threshold AMPDA activity 1,67 IU was characterized with the predictive value of negative results (without taking into account the prevalence) near 100%, Se 98%, Sp 62,45%.Cutoff value (CV) of ADA activity (9,57 IU) was characterized with LRN 0,104, Se 92,45%, Sp 72,65%, the sum (Se+Sp 165,10%), which was maximum not only for this test but for all the studied enzymes. The predictive value of negative results (without taking into account the prevalence) was 98,20%. The clinically significant CV of positive result for the ADA activity definition was identified also: LRP was 6,93 (Se 22,64%, Sp 96,73%) for the range of 12.58 IU and above. This fact allows the use of this test not only for the screening, but also, in some cases, for the verification of gout with significant pretest probability of this disease.Two CV were selected for the XDG activity: 7,49 μM/l×min (Se 47,17%, Sp 97,14%) and 8,39 μM /l×min (Se 39,62%, Sp 99,59%). The result of XDG activity determining in the range of 7.49 - 8.39 μM /l×min is an important argument in favor of the gout presence, but this may be useful for differential diagnosis only at high pretest probability of the gout.ConclusionsDetermination of the ADA activity was gave way to AMPDA activity determination at the gout screening and to XDG activity determination at gout verification. However, the ADA multifunctionality, evidenced clinically significant presence of the second CV (positive results) and a small proportion of the cases, which covered a “grey area” between CV (27.48%), provided the ability to use this marker as a backup in the absence of diagnostically relevant AMPDA and XDG activities.Disclosure of InterestNone declared