Performance characteristics of newer MIC gradient strip tests compared with the Etest for antimicrobial susceptibility testing of Neisseria gonorrhoeae AGNEZ J € ONSSON, 1 SUSANNE JACOBSSON, 1 SUNNIVA FOERSTER, 1 MICHELLE J. COLE 2 and MAGNUS UNEMO 1 1 WHO Collaborating Centre for Gonorrhoea and Other STIs, Department of Laboratory Medicine, Microbiology, Faculty of Medicine and Health, € Orebro University, € Orebro, Sweden; and 2 Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit, National Infection Service, Public Health England, London, UK J€ onsson A, Jacobsson S, Foerster S, Cole MJ, Unemo M. Performance characteristics of newer MIC gradient strip tests compared with the Etest for antimicrobial susceptibility testing of Neisseria gonorrhoeae. APMIS 2018. For Neisseria gonorrhoeae susceptibility testing, Etest, comparable to agar dilution, is frequently used. In recent years, newer MIC gradient strip tests have been commercialized. However, these tests have not been appropriately evaluated for gonococci. We evaluated the sensitivity, specificity, accuracy, quality, availability of antimicrobials and cost of the MIC Test Strip (Liofilchem), M.I.C.Evaluator (Oxoid) and Ezy MIC Strip (HiMedia), compared to the reference Etest (bioM erieux), for gonococcal susceptibility testing. The MICs of eight antimicrobials in 103 gonococcal international reference strains (n = 29) and clinical isolates (n = 74) were examined. Coefficient of determination (R 2 ), complete agreement, essential agreement, SIR categorical agreement, sensitivity, specificity and accuracy were calculated. R 2 of the MICs for the antimicrobials ranged between 0.674–0.996, 0.617–0.993, and 0.643–0.994 for the MIC Test Strip, M.I.C.Evaluator strips and Ezy MIC Strips respectively. The essential agreement (SIR categorical agreement) was 99.6% (88.6%), 100% (87.1%) and 93.0% (83.1%) respectively. M.I.C.Evaluator strips for gonococcal key antimicro- bials were lacking and the Ezy MIC Strips showed an inconsistent accuracy, quality and some strips were contami- nated. The Liofilchem MIC Test Strips had limitations, but might be relatively accurate alternatives to Etest for gonococci. Strict quality assurance (at manufacturing and testing laboratory), including quality controls, are required. Key words: gonorrhoea; Etest; MIC Test Strip (Liofilchem); M.I.C.Evaluator (Oxoid); Ezy MIC Strips (HiMedia); MIC gradient strip test. Magnus Unemo, WHO Collaborating Centre for Gonorrhoea and Other STIs, National Reference Laboratory for STIs, Department of Laboratory Medicine, Microbiology, € Orebro University Hospital, SE-701 85 € Orebro, Sweden. e-mail: magnus.unemo@regionorebrolan.se Neisseria gonorrhoeae, the aetiological agent of gon- orrhoea, has developed resistance to all antimicro- bials currently available for treatment, including the last-line extended-spectrum cephalosporin (ESC) ceftriaxone that currently is internationally recom- mended in first-line dual antimicrobial therapy together with azithromycin or monotherapy in some countries (1–4). Surveillance of antimicrobial resis- tance (AMR) in N. gonorrhoeae is essential globally. However, gonococcal AMR surveillance is lacking in many regions worldwide, which is a particular problem in many gonorrhoea high-burden regions that also in many cases are less-resourced settings. The AMR emergence and monitoring is further complicated in many settings by the high level of uncontrolled usage of antimicrobials, lack of treat- ment failure monitoring, slow update of treatment guidelines and absence of an accurate cost-effective method for AMR testing (1, 2, 4). For AMR testing, agar dilution technique for quantitative determination of minimum inhibitory concentration (MIC) of antimicrobials has been the gold standard method. However, particularly when examining lower numbers of isolates the Etest Received 15 January 2018. Accepted 7 August 2018 1 APMIS © 2018 APMIS. Published by John Wiley & Sons Ltd. DOI 10.1111/apm.12887 JOURNAL OF PATHOLOGY, MICROBIOLOGY AND IMMUNOLOGY