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Synovial Lactic Acid and Septic Arthritis—Reply

Synovial Lactic Acid and Septic Arthritis—Reply In Reply: Our search of the literature identified 6 studies1-5 that address synovial fluid lactic acid as a clinical test for septic arthritis. Previous studies6 suggest that although synovial lactic acid dehydrogenase (LDH) by enzymatic analysis may be sensitive for detecting bacterial infection, it is not specific, and elevated synovial LDH levels may be observed in noninfectious inflammatory and crystal-induced arthropathies, such as rheumatoid arthritis and gout. The identified studies were heterogeneous in their measurement of lactic acid. Brook et al,1 Gratacós et al,2 and Riordan et al5 evaluated lactic acid concentration by gas liquid chromatography, while Mossman et al3 and Shmerling et al4 assessed LDH by enzymatic analysis. Furthermore, Gratacós et al evaluated D-lactic acid, an optical isomer of L-lactic acid. The other studies did not identify if they were referring to D-lactic acid, L-lactic acid, or both. Most studies of synovial lactic acid were excluded from our meta-analysis because of their heterogeneity, and they did not evaluate a clinical test of interest. The studies by Shmerling et al4 were included because they were of high study quality and level of evidence. As stated in our article, the studies by Shmerling et al4 showed synovial LDH had 100% sensitivity but poor specificity with only half the cases being septic arthritis, resulting in many false-positive test results. These results may suggest that a low level of synovial fluid LDH would exclude the diagnosis of septic arthritis, but the negative likelihood ratio of 0.10 (95% confidence interval, 0.00-1.60) is not statistically significant. Gas liquid chromatography assay of lactic acid may be more useful than enzymatic analysis of LDH. Although there are limited data from small numbers of patients to support the usefulness of synovial lactic acid measurement, such as in Riordan et al,5 we believe that there is not enough evidence to encourage it as a routine test to diagnose septic arthritis at this time. However, synovial lactic acid estimation by gas liquid chromatography deserves further study. Back to top Article Information Financial Disclosures: None reported. References 1. Brook I, Reza MJ, Bricknell KS, Bluestone R, Finegold SM. Synovial fluid lactic acid: a diagnostic aid in septic arthritis. Arthritis Rheum. 1978;21(7):774-779697948Google ScholarCrossref 2. Gratacós J, Vila J, Moya F. et al. D-lactic acid in synovial fluid: a rapid diagnostic test for bacterial synovitis. J Rheumatol. 1995;22(8):1504-15087473474Google Scholar 3. Mossman SS, Coleman JM, Gow PJ. Synovial fluid lactic acid in septic arthritis. N Z Med J. 1981;93(678):115-1176943453Google Scholar 4. Shmerling RH, Delbanco TL, Tosteson AN, Trentham DE. Synovial fluid tests: what should be ordered? JAMA. 1990;264(8):1009-10142198352Google ScholarCrossref 5. Riordan T, Doyle D, Tabaqchali S. Synovial fluid lactic acid measurement in the diagnosis and management of septic arthritis. J Clin Pathol. 1982;35(4):390-3947076866Google ScholarCrossref 6. Gobelet C, Gerster JC. Synovial fluid lactate levels in septic and non-septic arthritides. Ann Rheum Dis. 1984;43(5):742-7456497466Google ScholarCrossref http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png JAMA American Medical Association

Synovial Lactic Acid and Septic Arthritis—Reply

JAMA , Volume 298 (1) – Jul 4, 2007

Synovial Lactic Acid and Septic Arthritis—Reply

Abstract

In Reply: Our search of the literature identified 6 studies1-5 that address synovial fluid lactic acid as a clinical test for septic arthritis. Previous studies6 suggest that although synovial lactic acid dehydrogenase (LDH) by enzymatic analysis may be sensitive for detecting bacterial infection, it is not specific, and elevated synovial LDH levels may be observed in noninfectious inflammatory and crystal-induced arthropathies, such as rheumatoid arthritis and gout. The identified studies...
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Publisher
American Medical Association
Copyright
Copyright © 2007 American Medical Association. All Rights Reserved.
ISSN
0098-7484
eISSN
1538-3598
DOI
10.1001/jama.298.1.40-b
Publisher site
See Article on Publisher Site

Abstract

In Reply: Our search of the literature identified 6 studies1-5 that address synovial fluid lactic acid as a clinical test for septic arthritis. Previous studies6 suggest that although synovial lactic acid dehydrogenase (LDH) by enzymatic analysis may be sensitive for detecting bacterial infection, it is not specific, and elevated synovial LDH levels may be observed in noninfectious inflammatory and crystal-induced arthropathies, such as rheumatoid arthritis and gout. The identified studies were heterogeneous in their measurement of lactic acid. Brook et al,1 Gratacós et al,2 and Riordan et al5 evaluated lactic acid concentration by gas liquid chromatography, while Mossman et al3 and Shmerling et al4 assessed LDH by enzymatic analysis. Furthermore, Gratacós et al evaluated D-lactic acid, an optical isomer of L-lactic acid. The other studies did not identify if they were referring to D-lactic acid, L-lactic acid, or both. Most studies of synovial lactic acid were excluded from our meta-analysis because of their heterogeneity, and they did not evaluate a clinical test of interest. The studies by Shmerling et al4 were included because they were of high study quality and level of evidence. As stated in our article, the studies by Shmerling et al4 showed synovial LDH had 100% sensitivity but poor specificity with only half the cases being septic arthritis, resulting in many false-positive test results. These results may suggest that a low level of synovial fluid LDH would exclude the diagnosis of septic arthritis, but the negative likelihood ratio of 0.10 (95% confidence interval, 0.00-1.60) is not statistically significant. Gas liquid chromatography assay of lactic acid may be more useful than enzymatic analysis of LDH. Although there are limited data from small numbers of patients to support the usefulness of synovial lactic acid measurement, such as in Riordan et al,5 we believe that there is not enough evidence to encourage it as a routine test to diagnose septic arthritis at this time. However, synovial lactic acid estimation by gas liquid chromatography deserves further study. Back to top Article Information Financial Disclosures: None reported. References 1. Brook I, Reza MJ, Bricknell KS, Bluestone R, Finegold SM. Synovial fluid lactic acid: a diagnostic aid in septic arthritis. Arthritis Rheum. 1978;21(7):774-779697948Google ScholarCrossref 2. Gratacós J, Vila J, Moya F. et al. D-lactic acid in synovial fluid: a rapid diagnostic test for bacterial synovitis. J Rheumatol. 1995;22(8):1504-15087473474Google Scholar 3. Mossman SS, Coleman JM, Gow PJ. Synovial fluid lactic acid in septic arthritis. N Z Med J. 1981;93(678):115-1176943453Google Scholar 4. Shmerling RH, Delbanco TL, Tosteson AN, Trentham DE. Synovial fluid tests: what should be ordered? JAMA. 1990;264(8):1009-10142198352Google ScholarCrossref 5. Riordan T, Doyle D, Tabaqchali S. Synovial fluid lactic acid measurement in the diagnosis and management of septic arthritis. J Clin Pathol. 1982;35(4):390-3947076866Google ScholarCrossref 6. Gobelet C, Gerster JC. Synovial fluid lactate levels in septic and non-septic arthritides. Ann Rheum Dis. 1984;43(5):742-7456497466Google ScholarCrossref

Journal

JAMAAmerican Medical Association

Published: Jul 4, 2007

References