EFFECT OF LONG-TERM STORAGE ON STABILITY OF ADENOSINE DEAMINASE (ADA) ACTIVITY IN PERITONEAL FLUID SAMPLE

Abstract

Introduction: Adenosine deaminase (ADA) activity in peritoneal fluid is a well-established diagnostic marker for tuberculous peritonitis. However, data on the stability of peritoneal fluid ADA during extended storage are limited, which has implications for retrospective studies and clinical research. Aim: To evaluate the effect of long-term storage in different temperature(room temperature, 2-4°C,-20°C,-80°C) on ADA activity in peritoneal fluid samples and is to determine the ideal storage temperature and time. Materials and Methods: This prospective observational study included 31 peritoneal fluid samples were enrolled in the study form Central Biochemistry Laboratory(CBL) after completion of routine requested diagnostic tests. Samples were immediately processed at baseline(<1 hour of sample collection) and compared with values obtained after storage at room temperature(22-24°C), 2-4°C,-20°C,-80°C for 1 day,7 days,30 days,60 days, and 180 days. ADA was estimated using the enzymatic method(Erba Manneim, india) on an automated analyzer. Repeated-measures ANOVA with Bonferroni correction was used for statistical analysis. Results: Mean baseline ADA activity was 53.75±14.37 U/L. ADA activity showed a significant decline of 11.79 ± 4.42 IU/L(p<0.01) at Day 180 stored in room temperature(RT). These data indicate marked loss of enzyme activity during prolonged ambient storage. Slight variation in the ADA activity at 2-4°C as compared to RT. ADA activity remained stable from day 1 to 180 days at -20°C and -80°C of storage (mean percentage change is <5.8 from baseline; p>0.05). Conclusion: Peritoneal fluid ADA activity is stable from day 1 to 180 days when stored at -20°C and -80°C. The ADA activity is deteriorated significantly in RT and slightly deteriorated in 2-4°C. Ideal recommended storage temperature and time is -20°C, and -80°C