Utility of Ascitic Fluid Adenosine Deaminase Levels in the Diagnosis of Tuberculous Peritonitis in General Medical Practice

Our plain-English summary of Utility of Ascitic Fluid Adenosine Deaminase Levels in the Diagnosis of Tuberculous Peritonitis in General Medical Practice, by A. Kumabe, S. Hatakeyama, N. Kanda, et al (The Canadian Journal of Infectious Diseases & Medical Microbiology = Journal Canadien des Maladies Infectieuses et de la Microbiologie Médicale, 2020).

The study

• Authors: A. Kumabe, S. Hatakeyama, N. Kanda, Y. Yamamoto, M. Matsumura
• Journal: The Canadian Journal of Infectious Diseases & Medical Microbiology = Journal Canadien des Maladies Infectieuses et de la Microbiologie Médicale
• Published: 2020;2020:5792937
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Tuberculous peritonitis is difficult to diagnose due to its varying clinical features, in addition to the low yield on bacterial culture or polymerase chain reaction using ascitic fluid samples. This study aimed to investigate the sensitivity and specificity of elevated adenosine deaminase (ADA) levels as a diagnostic marker for tuberculous peritonitis.

Methods: A retrospective cohort of 181 adult patients who underwent ascitic fluid ADA level examination at Jichi Medical University Hospital between January 2006 and December 2015 were included. We collected data regarding ascitic fluid analyses including ADA levels, bacteriology and cytology, final diagnosis (cause of ascites), basis of the diagnosis, duration to diagnosis, and disease outcome.

Results: Among 181 patients, elevated ascitic ADA levels (≥40 IU/L) were observed in 15 patients (median, 87.2 IU/L; range, 44.0-176.1 IU/L); 8 patients had tuberculous peritonitis, 4 had lymphoma-related ascites, and 2,had peritoneal carcinomatosis with bacterial coinfection, and 1 had chlamydial pelvic inflammatory disease. Among 166 patients without ascitic ADA level elevation (median, 7.3 IU/L; range, <2.0-39.1 IU/L), none had tuberculosis, 4 had lymphoma-related ascites, 28 had cancer/mesothelioma-related ascites, and 134 had ascites due to other causes. In our cohort, elevated ascitic fluid ADA levels (≥40 IU/L) showed 100% sensitivity, 96.0% specificity, 53.3% positive predictive value (PPV), and 100% negative predictive value for the diagnosis of peritoneal tuberculosis.

Conclusions: Ascitic fluid ADA levels ≥40 IU/L showed excellent sensitivity, despite a low PPV, for the diagnosis of tuberculous peritonitis. Lymphoma-related ascites is an important mimic of tuberculous peritonitis that can result in high ascitic fluid ADA levels with similar clinical manifestations.

Copyright © 2020 Ayako Kumabe et al.

In plain English

This retrospective study from Jichi Medical University Hospital in Japan was not a study of asbestos. It examined whether a laboratory test, adenosine deaminase (ADA) measured in abdominal fluid (ascites), helps diagnose tuberculous peritonitis, a tuberculosis infection of the abdominal lining. The authors reviewed the records of 181 adult patients tested between January 2006 and December 2015, using a cut-off of 40 IU/L. Fifteen patients had raised ADA. Of these, 8 had tuberculous peritonitis, 4 had lymphoma-related ascites, 2 had cancer that had spread to the abdominal lining (peritoneal carcinomatosis) with bacterial infection, and 1 had chlamydial pelvic inflammatory disease. None of the 166 patients below the cut-off had tuberculosis. The test showed 100% sensitivity, 96.0% specificity and a 53.3% positive predictive value. Among 40 patients with carcinoma, lymphoma or mesothelioma, 6 had raised ADA. The one patient listed with peritoneal mesothelioma had a level below 40 IU/L. The authors concluded that ADA levels of 40 IU/L or more showed excellent sensitivity, and that lymphoma can produce high levels with similar symptoms. They noted the study was small, single-centre and possibly affected by detection bias.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective observational (cohort) study of a diagnostic test
• Who was studied: 181 adult patients who had ascitic fluid ADA measured at Jichi Medical University Hospital, Japan, between January 2006 and December 2015. Median age was 62 years and 100 (55.2%) were male. Children were excluded.
• Exposure: No asbestos or other exposure was studied. The study evaluated a laboratory test: adenosine deaminase in ascitic fluid, with a cut-off of 40 IU/L.
• Main results:
  • 15 of the 181 patients had ascitic ADA of 40 IU/L or more (median 87.2 IU/L; range 44.0 to 176.1 IU/L).
  • Among the 15 patients with high ADA, 8 (53.3%) had tuberculous peritonitis, 4 (26.7%) had lymphoma-related ascites, 2 (13.3%) had peritoneal carcinomatosis with bacterial infection, and 1 (6.7%) had chlamydial pelvic inflammatory disease.
  • Of the 2 patients with peritoneal carcinomatosis and bacterial coinfection, one had ovarian cancer and the other had cancer of unknown primary site.
  • None of the 166 patients with ascitic ADA below 40 IU/L had tuberculosis.
  • For diagnosing peritoneal tuberculosis, ADA of 40 IU/L or more showed 100% sensitivity, 96.0% specificity, 53.3% positive predictive value and 100% negative predictive value.
  • In the 8 tuberculosis patients, ascitic fluid culture was positive in 2 of 8, the acid-fast bacilli smear in 0 of 8, and the tuberculosis PCR test in 0 of 6.
  • Elevated ascitic ADA was seen in 50.0% of patients diagnosed with lymphoma and 25.0% of those diagnosed with ovarian cancer.
  • Among lymphoma patients, the mortality rate was 100% in those with elevated ADA and 50.0% in those without.
  • Table 3 lists one patient with peritoneal mesothelioma, whose ascitic ADA was below 40 IU/L.
• The authors' conclusion: The authors concluded that ascitic fluid ADA levels of 40 IU/L or more showed excellent sensitivity for tuberculous peritonitis, despite a relatively low specificity (the abstract says low positive predictive value). They added that both tuberculosis and lymphoma can produce high ascitic ADA with similar clinical features.
• Limitations the authors state:
  • The study was retrospective, single-centre, and included a relatively small number of adult patients.
  • Detection or ascertainment bias may be present, because physicians tend to order ADA tests when they already suspect tuberculosis.
  • One patient was diagnosed with peritoneal tuberculosis on clinical grounds only, without histological or bacteriological evidence. The authors said this means specificity might be overestimated.

Topics

Medical terms in this study, explained in our Lexicon: Cytology, Ascites, Mesothelioma.

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