New insights, only from BakoDx

Onychodystrophy PCR Test with Terbinafine Resistance

Know before you treat

  • Eliminate terbinafine “watchful waiting” period

  • Avoid unnecessary medications & potential side effects

  • Increase treatment efficacy & patient satisfaction

While terbinafine is most often prescribed for onychomycosis caused by dermatophytic fungi, an increasing rate of cases with terbinafine resistance may be impeding treatment success.

To date, 12 specific genetic mutations have been identified in Trichophyton genera, primarily T. rubrum and T. mentagrophytes complex, which confer terbinafine resistance.

The new BakoDx Onychodystrophy PCR test with terbinafine resistance enables you to understand the likelihood of treatment effectiveness in days, instead of months.

Request more info

How does BakoDx lab testing impact therapy outcomes, especially if a patient’s fungus is terbinafine-resistant?

Drag the slider right to see the Bako difference:

BakoDx Definitive Diagnosis

(1) Sigurgeirsson B, Olafsson JH, Steinsson JB, Paul C, Billstein S, Evans EG. Long-term Effectiveness of Treatment With Terbinafine vs Itraconazole in Onychomycosis: a 5-year blinded prospective follow-up study. Arch Dermatology 2002; 138:353–357.

Compare Fungal Nail Tests for Terbinafine Resistance

BakoDx Terbinafine Test Comparison

Click image to enlarge

While superficial onychomycosis caused by Trichophyton rubrum and T. mentagrophytes can often be treated with terbinafine, an increasing rate of cases with antifungal resistance mutations is impeding treatment success.

There is a serious global public health concern that antifungal treatment, traditionally oral and/or topical terbinafine, may be ineffective against 12 resistant mutation strains found in members of the Trichophyton genera.

BakoDx’s highly experienced molecular analysis team developed an advanced real-time PCR terbinafine resistance reflex to seamlessly integrate with our Onychodystrophy PCR test to accurately detect when 12 terbinafine resistant mutations are present in T. rubrum and T. mentagrophytes.

  • At initial presentation of nail dystrophy
  • When considering terbinafine therapy
  • Cases of treatment failure


Just as the current onychodystrophy test provides cost effectiveness through a proprietary reflex algorithm, this new addition will only reflex to terbinafine resistance when it identifies T. rubrum and/or T. mentagrophytes. Furthermore, our test is able to detect 12 current mutations in just four reactions. BakoDx is contracted with most insurance plans throughout the United States, providing clients and their patients with a superior level of access to testing services.

Terbinafine treatment failure may occur in patients with terbinafine resistant strains of dermatophytic fungi. Many times, despite having a positive T. rubrum or T. mentagrophytes diagnosis, patients do not improve. In these cases, where there is a poor response or non-responsiveness to the recommended antifungal, patients may grow frustrated, lose valuable time with unnecessary treatment and incur added Rx costs. In addition, there are secondary bacterial infections, which are potentially the most significant complication leading to adverse outcomes.

The Growing Problem of Antifungal Resistance in Onychomycosis and Other Superficial Mycoses

Gupta, A.K., Renaud, H.J., Quinlan, E.M. et al. The Growing Problem of Antifungal Resistance in Onychomycosis and Other Superficial Mycoses. Am J Clin Dermatol 22, 149–157 (2021).


Superficial mycoses are becoming increasingly resistant to current antifungal medications. As alternative therapeutic options are limited, the increasing frequency of reports of antifungal resistance is alarming. This epidemic parallels the rise of antibiotic resistance; however, the significance of this problem has yet to gain global attention. Here, we discuss the reports of antifungal resistance from around the world, present our own experience with treatment-resistant infections, and examine alternative treatment strategies. The majority of reports of recalcitrant infections indicate terbinafine resistance as the causative factor. Single-point mutations in the squalene oxidase gene is the most reported mechanism of resistance to terbinafine. Mixed infections of dermatophytes with non-dermatophyte molds and/or yeasts are becoming more prevalent and contributing to the resistant nature of these infections.

The key to selecting an effective antifungal therapy for a recalcitrant infection is identification of the infectious organisms(s) and testing susceptibility of the organism(s) to antifungal drugs. Combination and sequential therapy regimens are options, but both require active monitoring for hepatic and renal function, drug interactions, and other adverse effects. Selected topical antifungals with a wide spectrum of activity may also be considerations in some clinical presentations. Innovative treatment regimens and novel therapeutics are needed to overcome the rising epidemic of antifungal resistance.

Learn more about BakoDx Terbinafine Resistance testing

*Please note the terbinafine resistance reflex is currently unavailable in NY.