Point-of-care testing (POCT) allows clinicians to confirm a diagnosis and determine a management plan in a more timely fashion than offsite laboratory testing.1 Common examples of POCT include pregnancy testing or blood glucose screening.
In eye care, two devices clearly fall under the guise of POCT: AdenoPlus (Rapid Pathogen Screening, Inc./NicOx) for adenovirus detection and the TearLab Osmolarity System (TearLab Corporation) for dry eye evaluation. Here, we’ll review how you can deliver enhanced patient care with these POCT-based diagnostic systems.
We’ve all heard about instances when entire clinics have been shut down because a bout of epidemic keratoconjunctivitis (EKC) affected its doctors and staff.2 Without question, EKC is one of the most severe forms of conjunctivitis we face. The disease couse has a long duration––with an active infection persisting for seven days, followed by an immune response and the presence of sub-epithelial infiltrates for another six to seven days, concluding with five to seven additional days of morbidity.2,3 In fact, research has shown that it could take as long as 24 weeks for an EKC patient to exhibit normal stromal characteristics.3
So, it is essential to make a prompt diagnosis and begin treatment immediately to decrease the infectious potential of EKC as well as limit its associated complications, such as decreased vision secondary to sub-epithelial infiltrative progression.4,5 Because many signs and symptoms of viral conjunctivitis mimic those of bacterial conjunctivitis, making a diagnosis can be difficult. Further, misappropriated antibiotic treatment of a viral conjunctivitis not only will yield little therapeutic effect, but also increase the probability of localized resistance.
The AdenoPlus procedure involves touching a felt pad to the lower bulbar conjunctiva, which allows it to absorb tears. Then, the saturated pad is snapped into a cartridge. A liquid reagent subsequently is applied and absorbed into the system. After five to 10 minutes, the result will be available for review. A single line in the reading window indicates a negative result for adenovirus, whereas two lines support a positive adenovirus diagnosis.
When a patient initially presents with acute red eye, instruct your staff to take a history and then administer the AdenoPlus test. The results will be ready by the time you see the patient, which helps increase examination efficiency as well as enhance your patient’s trust in your diagnosis. Look for pseudomembranes and other potential findings associated with EKC to complete the examination. Then, treat the patient with topical antivirals, such as Zirgan (ganciclovir ophthalmic gel, Bausch + Lomb) or a povidone iodine rinse.
Another helpful POCT-based technology is the TearLab Osmolarity System. This device employs a single-use cartridge that houses a gold-plated microchip, a handpiece and a reader. By touching the edge of the tears at the temporal aspect of the lower eyelid, the device measures osmolarity in seconds. You only need to collect a 50nL tear sample to test even the most severe Sjögren’s syndrome patients.6,7
Tear film osmolarity demonstrates the least variability of all dry eye metrics and is a fundamental consideration in any dry eye disease work-up.8-12 Once a small sample of tears is collected, TearLab determines the osmolarity reading in milliosmoles per liter (mOsmol/L).
A reading between 300mOsmol/L and 320mOsmol/L is considered mild dry eye; 320mOsmol/L to 340mOsmol/L suggests moderate dry eye; and any finding greater than 340mOsmol/L is graded as severe dry eye.9,11 If the difference between eyes is greater than 6mOsmol/L, and a reading greater than 300mOsmol/L is documented in at least one eye, the patient likely has dry eye disease. This is because the eyes of patients with dry eye constantly remain in flux, as one eye tries to compensate for the deficiencies of the other.13
The TearLab test has a positive predictive value of 87%, which is almost double that of any other commercially available dry eye measurement––including tear film break-up time, Schirmer testing or subjective patient questionnaires.11 Additionally, TearLab testing is reimbursed by CMS at approximately $43 per patient.
The Future of POCT
Although POCT is highly valuable to clinical diagnosis and management, AdenoPlus and TearLab are just the beginning. Companies are developing POCT devices that may identify Alzheimer’s plaques in the crystalline lens years or even decades before they appear in the brain.14 Other devices that screen for allergic conjunctivitis via IgE testing or inflammatory eye disease via MMP marker detection are being developed as well.15,16 And, in the near future, we may gain access to POCT testing devices that detect and evaluate systemic biomarkers for diabetic eye disease in a patient’s tears.17
With the addition of POCT devices in clinical practice, optometrists will be able to play an increased role in providing both primary eye care and medical care to their patients. In turn, POCT will further enhance patients’ confidence in your diagnostic capabilities.
Dr. Karpecki is a paid consultant to NicOx and Bausch + Lomb. He also serves on the board of directors and clinical advisory board for TearLab.
1. Hovis JK, Ramaswamy S. The effect of test distance on the CN lantern results. Vis Neurosci. 2006 May-Aug;23(3-4):675-9.
2. Jernigan JA, Lowry BS, Hayden FG, et al. Adenovirus type 8 epidemic keratoconjunctivitis in an eye clinic: risk factors and control. J Infect Dis. 1993 Jun;167(6):1307-13.
3. Dosso AA, Rungger-Brandle E. Clinical course of epidemic keratoconjunctivitis: evaluation by in vivo confocal microscopy. Cornea. 2008 Apr;27(3):263-8.
4. Kaufman HE, Haw WH. Ganciclovir ophthalmic gel 0.15%: safety and efficacy of a new treatment for herpes simplex keratitis. Curr Eye Res. 2012 Jul;37(7):654-60.
5. Trinauarat A, Atchaneeyasakul LO. Treatment of epidemic keratoconjunctivitis with 2% povidone-iodine: a pilot study. J Ocul Pharmacol Ther. 2012 Feb;28(1):53-8.
6. Bunya VY, Langelier N, Chen S. Tear Osmolarity in Sjögren Syndrome. Cornea. 2013 Feb 12. [Epub ahead of print]
7. Lemp MA, Foulks GN, Pepose JS. Evaluation of tear osmolarity in non-Sjögren and Sjögren Syndrome dry eye patients with the TearLab system. Cornea. 2013 Mar;32(3):379-81.
8. Versura P, Campos EC. TearLab Osmolarity System for diagnosing dry eye. Expert Rev Mol Diagn. 2013 Mar;13(2):119-29.
9. Sullivan BD, Crews LA, Sonmez B, et al. Clinical utility of objective tests for dry eye disease: variability over time and implications for clinical trials and disease management. Cornea. 2012 Sep;31(9):1000-8.
10. Eperiesi F, Auila M, Bartlett H, et al. Reproducibility and repeatability of the OcuSense TearLab osmometer. Graefes Arch Clin Exp Ophthalmol. 2012 Aug;250(8):1201-5.
11. Sullivan BD, Whitmer D, Nichols KK, et al. An objective approach to dry eye disease severity. Invest Ophthalmol Vis Sci. 2010 Dec;51(12):6125-30.
12. The definition and classification of dry eye disease: Report of the Definition and Classification Subcommittee of the International Dry Eye WorkShop (2007). Ocul Surf. 2007 Apr;5(2):75-92.
13. Gaffney EA, Tiffany JM, Yokoi N et al. A mass and solute balance model for tear volume and osmolarity in the normal and the dry eye. Prog Retin Eye Res. 2010 Jan;29(1):59-78.
14. Ecroyd H, Carver JA. Crystallin proteins and amyloid fibrils. Cell Mol Life Sci. 2009 Jan;66(1):62-81.
15. Doan S, Belayachi N, Ren L. Tear IgE level measurement using semiquantitative methods in children with vernal keratoconjunctivitis (VKC). Available at: http://abstracts.iovs.org/cgi/content/abstract/43/12/114. Accessed April 4, 2013.
16. Rapid Pathogen Screening, Inc. RPS InflammaDry Detector. Available at: www.rpsdetectors.com/in/wp-content/uploads/2012/07/FORM-MKT-003.1-RPS-InflammaDry-Detector-Sell-Sheet.pdf. Accessed April 4, 2013.
17. Csosz E, Boross P, Csutak A, et al. Quantitative analysis of proteins in the tear fluid of patients with diabetic retinopathy. J Proteomics. 2012 Apr 3;75(7):2196-204.