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Objectives: Serum angiotensin-converting enzyme (ACE) is the only biomarker routinely used in the laboratory diagnostics of sarcoidosis, and ACE inhibitor (ACEi) drugs are among the most prescribed drugs worldwide. Taking ACEi can mislead medical teams by lowering ACE activity, delaying diagnosis and giving a false impression of disease activity of sarcoidosis. We aimed to develop a simple method to detect the presence of ACEi drugs in samples, to investigate the ACEi medication-caused interference and consequences in a retrospective study., Methods: ACE activity and the level of ACE inhibition were determined for 1823 patients with suspected sarcoidosis. These values were compared with the therapeutic information at the first and follow-up visits., Results: A total of 302 patients had biochemical evidence of an ACEi drug effect during diagnostic ACE activity testing. In their case, ACE activity was significantly lower (median(IQR): 4.41 U/L(2.93-6.72)) than in patients not taking ACEi (11.32 U/L(8.79-13.92), p<0.01). In 62 sarcoidosis patients, the ACEi reduced ACE activity to the reference range or below. Only in 40 % of the cases was the medication list recorded in the outpatient chart and only in 3 cases was low ACE activity associated with ACEi use. 67 % of the repeated ACE activity measurements were also performed during ACEi therapy., Conclusions: Our study revealed that the use of ACEi is common in patients with suspected sarcoidosis. The ACE activity lowering effect of ACEi drugs may escape the attention of medical teams which can lead to diagnostic errors and unnecessary tests. Nevertheless, these pitfalls can be avoided by using a method suggested by our team., (© 2024 the author(s), published by De Gruyter, Berlin/Boston.)

Serum chitotriosidase (CTO) activity was proposed as a biomarker in sarcoidosis being potentially useful in diagnostics. Nevertheless, a common duplication polymorphism (c.1049&#95;1072dup24, Dup24) of the CTO gene influences CTO activity and thereby compromises its use in sarcoidosis. Here we aimed to substitute CTO activity with CTO concentration to prevent the confounding effect of Dup24. CTO activity, concentration and genetic backgrounds were determined in 80 histopathology proven sarcoidosis patients and 133 healthy individuals. CTO activities were lower in healthy individuals and sarcoidosis patients heterozygous for Dup24 mutation (472 ± 367 mU/L, n = 49; 2300 ± 2105 mU/L, n = 29) than in homozygous wild types (838 ± 856 mU/L, n = 81; 5125 ± 4802 mU/L, n = 48; p < 0.001, respectively). Sera of Dup24 homozygous individuals had no CTO activity. CTO concentrations were also lower in healthy individuals and sarcoidosis patients heterozygous for Dup24 mutation (7.2 ± 1.9 µg/L, n = 11; 63.16 ± 56.5 µg/L, n = 29) than in homozygous wild types (18.9 ± 13.0 µg/L, n = 36; 157.1 ± 132.4 µg/L, n = 47, p < 0.001, respectively) suggestive for an interaction between Dup24 mutation and CTO concentration determinations. We also identified a healthy Hungarian male subject without CTO activity carrying a rare mutation (c.(965&#95;993)del), which mutation has been considered unique for Cypriot population to date. Taken together, CTO concentration determination does not add to the CTO activity measurement when CTO is used as a biomarker in sarcoidosis. Therefore, genotyping of CTO gene should be involved in the interpretation of laboratory findings., (Copyright © 2020 The Author(s). Published by Elsevier B.V. All rights reserved.)

Establishing the diagnosis of sarcoidosis most often requires biopsy and histopathologic evaluation, since there is no single marker with sufficient specificity and sensitivity for the disease. Our aims were to determine and compare the diagnostic accuracies of several potential biomarkers and to develop a combined biomarker analysis tool for the diagnosis of sarcoidosis. 133 healthy individuals and 104 patients with suspected sarcoidosis and diagnostic thoracic surgery were enrolled into this study. Histopathologic results were contrasted to biomarker levels of chitotriosidase (CTO), serum amyloid-A (SAA), soluble interleukin-2 receptor (sIL-2R), lysozyme (LZM) or angiotensin converting enzyme (ACE). Sarcoidosis was confirmed by histopathology in 69 patients. CTO activity, sIL-2R concentration and ACE activity could discriminate between sarcoidosis and control patients, while SAA and LZM concentrations could not. A new combined parameter, which was derived from the multiplication of ACE by CTO activities (double product) showed the best diagnostic accuracy in this clinical study: (AUC = 0.898, sensitivity: 90.5%, specificity: 79.3%, positive and negative predictive values: 90.5% and 79.3%, respectively). Sarcoidosis can be diagnosed with the combined analysis of ACE and CTO activities more accurately than with single serum biomarkers in the absence of invasive biopsy in the majority of cases with pulmonary manifestation of sarcoidosis., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Serum angiotensin-converting enzyme (ACE) activity determination can aid the early diagnosis of sarcoidosis. We aimed to optimize a fluorescent kinetic assay for ACE activity by screening the confounding effects of endogenous ACE inhibitors and interfering factors. Genotype-dependent and genotype-independent reference values of ACE activity were established, and their diagnostic accuracies were validated in a clinical study., Methods: Internally quenched fluorescent substrate, Abz-FRK(Dnp)P-OH was used for ACE-activity measurements. A total of 201 healthy individuals and 59 presumably sarcoidotic patients were enrolled into this study. ACE activity and insertion/deletion (I/D) genotype of the ACE gene were determined., Results: Here we report that serum samples should be diluted at least 35-fold to eliminate the endogenous inhibitor effect of albumin. No significant interferences were detected: up to a triglyceride concentration of 16 mM, a hemoglobin concentration of 0.71 g/L and a bilirubin concentration of 150 μM. Genotype-dependent reference intervals were considered as 3.76-11.25 U/L, 5.22-11.59 U/L, 7.19-14.84 U/L for II, ID and DD genotypes, respectively. I/D genotype-independent reference interval was established as 4.85-13.79 U/L. An ACE activity value was considered positive for sarcoidosis when it exceeded the upper limit of the reference interval. The optimized assay with genotype-dependent reference ranges resulted in 42.5% sensitivity, 100% specificity, 100% positive predictive value and 32.4% negative predictive value in the clinical study, whereas the genotype-independent reference range proved to have inferior diagnostic efficiency., Conclusions: An optimized fluorescent kinetic assay of serum ACE activity combined with ACE I/D genotype determination is an alternative to invasive biopsy for confirming the diagnosis of sarcoidosis in a significant percentage of patients.