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'Threshold to treat' calculator may be more useful in clinical settings
When considering the use of risk calculators to inform treatment options, researchers reported in the Journal of Glaucoma that a “threshold to treat” computation may be useful in patient care.
Jampel and colleagues stated that the calculation could provide information to help evaluate the risk a patient with elevated intraocular pressure has in developing visual field damage.
"One important outcome of the Ocular Hypertension Treatment Study (OHTS) and the European Glaucoma Prevention Study was the development of risk calculators to help predict the likelihood of an individual with elevated intraocular pressure to develop glaucomatous optic nerve and/or visual field damage," they said. "The 5-year percentage risk of developing glaucoma is useful, but in a typical clinical setting, it may not be the most important information that can be derived from a risk calculator.
"We call this IOP level the threshold to treat and define it as the IOP at which the eye care practitioner and the patient conclude that the benefits of IOP lowering exceed the downside,” they continued. “The threshold to treat is dependent upon the level of risk that the patient and doctor are willing to tolerate in the absence of treatment."
Researchers assessed the level of risk that ophthalmologists will tolerate in untreated patients with ocular hypertension.
"Using simulated case scenarios consistent with the population of the OHTS, we determined that the average treatment threshold for 56 glaucoma specialists was a 23% chance of developing glaucoma over a 5-year period when they did not have the results of a risk calculator and 17% when they were provided with the risk calculator before making their decision. We also assessed the behavior of comprehensive ophthalmologists without glaucoma subspecialty training and determined the average risk threshold for treating a younger group and an older group of patients. The calculated risk threshold for glaucoma-trained physicians was 22% without a risk calculator and 17% with a risk calculator, and that for nonglaucoma-trained physicians was 16% without a risk calculator and 13% with a risk calculator."
They also found that doctors were more likely to treat 40- to 50-year-old patients compared to 70- to 80-year-old patients.
The authors concluded: "We hope that the threshold-to-treat calculator, available at http://oil.wilmer.jhu.edu/threshold, can provide information complementary to the traditional OHTS risk calculators, that will prove useful in patient care."
Disclosure: The authors have no financial disclosures.
Perspective
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Current Ocular Hypertension Treatment Study-based glaucoma risk calculators use patient information (age, IOP, central corneal thickness, cup-to-disc ratio and visual field pattern standard deviation) to derive a 5-year risk of developing glaucoma.
Jampel and colleagues take this a step further by posing the question: “At what IOP would you consider treatment if all the other variables are the same?”
Their threshold to treat calculator uses the same statistical principles to determine a cut-off IOP associated with an acceptable 5-year risk of developing glaucoma. This IOP is the threshold at which the patient and doctor would need to begin treatment, taking into consideration their risk tolerance.
This twist on the current glaucoma risk calculators is a potentially useful clinical tool, as the doctor and patient can plan ahead and prepare for possible treatment if the cut-off IOP is reached.
The threshold to treat calculator has limitations similar to the current risk calculators, but it makes the patient-doctor determine what risk they are comfortable with, which may also change as the patient ages.