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Point-of-service tests may complement approach to dry eye patients
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You have all seen this scene before. The eager student asks the teacher: “Master, should I strive for accuracy or should I try to be faster?” You know what is coming as soon as the Master raises the student’s chin with his hand. “Yes,” the Master answers with an inscrutable smile.
Whether you are a well-established dry eye expert or just considering adding a dry eye service to your clinic’s offerings, the list of questions you will need to answer just got a little bit longer. Should your clinic have TearLab tear osmolarity (TearLab Corporation) or the recently approved and CLIA-waived InflammaDry (RPS)? The short answer is “yes.” It is not possible in this day and age to provide the highest-quality care for dry eye syndrome (DES) or ocular surface disease (OSD) without having one or the other of these important tests. Like most modern care paradigms, the care of DES/OSD now includes all three of the elements in the three-pronged approach to modern medical care: high-tech diagnostic testing, pathology-specific treatment and the skills of a well-trained physician. Indeed, “yes” might mean both.
First point-of-service test for DES
Approved in 2010 and CLIA-waived in 2011, TearLab ushered in the era of point-of-service testing for DES. Mike Lemp, MD, the “father of dry eye,” did the seminal work that showed the relationship between elevated tear osmolarity (TO) and DES. Subsequent studies have shown that elevated TO contributes to both cellular damage and up-regulation of inflammation on the ocular surface. TO correlates more closely with DES symptoms than older measures. In addition, abnormal TO is diagnostic even in the absence of symptoms. The TearLab instrument can be used to assess the presence of occult DES in the presurgical setting for both cataract and laser refractive patients in order to allow treatment to prevent postoperative issues related to dryness.
Checking TO with the TearLab instrument is simple and efficient. Adding TO to the diagnostic protocol has almost no effect on the efficiency of seeing DES patients. At SkyVision, we have standing orders for TO testing to be performed on new patients who meet the criteria for a DES/OSD work-up. Our technicians perform the test before any other tests or drops are applied, and this information is already on the chart when the patient is seen by the ophthalmologist or optometrist. The TearLab instrument is classically used initially as a diagnostic instrument that gives values to determine “normal” or “abnormal.” Any reading less than 300 with inter-eye consistency is considered normal. A reading greater than 300 or an inter-eye difference greater than 8 is considered abnormal, signifying dry eye. Most clinics also use these readings to quantify the degree of dryness.
Newer test
Newer on the scene is InflammaDry. Approved in late 2013, it was recently CLIA-waived in the U.S., making it more widely available. This point-of-service test measures the presence and, to some extent, the degree of matrix metalloproteinase-9 (MMP-9) activity on the surface of the eye. MMP-9 levels are noted to be elevated in the presence of high TO, and higher levels of MMP-9 are correlated with moderate to severe symptoms on the Report of the International Dry Eye WorkShop. In a study included in the research that led to the U.S. Food and Drug Administration approval of InflammaDry, the test was shown to have a sensitivity of 85% and a specificity of 94% in the diagnosis of DES.
InflammaDry uses the same technical process we have all learned to use with the AdenoPlus test (marketed in the U.S. by Nicox) for adenovirus in acute conjunctivitis. A small sample of a patient’s tears is obtained, usually by a technician, and the InflammaDry unit produces a result in approximately 10 minutes. If you are doing both a TO test and InflammaDry on a patient, you should do the TO test first. While a positive result is not expressed in numerical units, the intensity of the positive result is generally thought to be proportional to the level of MMP-9 present: The brighter the stripe, the more MMP-9 activity is present.
Working with both tests
Which test should be part of your DES protocol? Is it the more established test, TearLab? Or is it the newer test, InflammaDry? Or is it both? The answer will depend in part on the degree of commitment a practice makes to diagnosing and treating DES. Both tests appear to be able to make the diagnosis of DES in the relative absence of other more classic signs (such as vital dye staining), and both tests also appear to be able to diagnose DES in the absence of obvious patient symptoms (in preop patients, for example). The TO test seems on first blush to be more helpful in determining the severity of DES, while InflammaDry by definition points you in the direction of treatment when it is positive.
While it is technically simple to perform both tests, and possible to incorporate either or both into your DES protocol, learning how to use the results as you make a diagnosis and formulate a treatment plan is actually rather complex. How will you interpret a “normal” TO or InflammaDry in the presence of DES symptoms and signs? Will the degree of “abnormal” influence your treatment decision? As you develop your therapeutic matrix, how will you interpret conflicting results from the two tests? Because the tests measure different aspects of DES, at what point in the ongoing care of your patients will you repeat each or both? There are a number of nuances involved in using the results of both tests. Pick one to start and really learn the ins and outs of that test before adding the second.
If you have yet to commit to either technology, it may make some sense to investigate the reimbursement atmosphere in your particular neck of the woods and start with the test that has the better coverage. It is important to remove any overt or covert barriers to making the tests a part of your standard operating procedure, and if the cost of doing the test is greater than your average reimbursement, there will be concerns among your staff members about doing something that will lose money; they may not feel empowered to actually do the test regardless of your instructions.
We have been using TearLab since late 2010, and it has become a core test in our DES protocol. As a group we feel that we have a deep understanding of how to use the results we obtain in both making a diagnosis and formulating a treatment plan. SkyVision will add InflammaDry to the mix now that it is available, and we will begin to evaluate the information that it provides in our DES protocols. I expect that, like TearLab and TO, the measurement of MMP-9 levels with InflammaDry will make me a better dry eye doc.