Ocular Tonometry and Sporadic Creutzfeldt - Jakob disease (sCJD): A Confirmatory Case-Control Study
Zoreh Davanipour *
Department of Neurology, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA and Current affiliation: Friends Research Institute, Los Angeles, CA, USA.
Eugene Sobel
Department of Neurology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA and Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA and Current affiliation: Friends Research Institute, Los Angeles, CA, USA.
Argyrios Ziogas
Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA and Current affiliation: University of California-Irvine, Irvine, CA, USA.
Carey Smoak
Department of Neurology, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA and Current affiliation: Roche Molecular Systems, Pleasanton, CA, USA.
Thomas Bohr
Department of Neurology, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA and Current affiliation: Jerry L Pettis VA Medical Center, Loma Linda, CA, USA.
Keith Doram
Department of Internal Medicine, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA and Current affiliation: Adventist Health, Roseville, CA, USA.
Boleslaw Liwnicz
Department of Pathology, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA.
*Author to whom correspondence should be addressed.
Abstract
Aims: To evaluate the hypothesis that sporadic Creutzfeldt-Jakob disease (sCJD) may be transmitted through ocular tonometry.
Background: The infectious agent of sCJD may be present in the cornea prior to clinical symptoms. Cornea infectiousness has been documented by cornea transplants in guinea pigs and humans. sCJD is resistant to complete inactivity by conventional sterilization techniques. Thus contact tonometry equipment is not disinfected sufficiently to kill sCJD. We previously hypothesized that contact tonometry is a sCJD risk factor.
Study Design: Population-based case-control study.
Place and Duration of Study: Department of Neurology, School of Medicine, Loma Linda University, Loma Linda, CA, USA; 4 years.
Methodology: An 11-state case-control study of pathologically confirmed definite sCJD cases, individually matched controls, and a sample of control surrogates was conducted. Ocular tonometry histories were obtained from case-surrogates, controls, and a sample of control-surrogates.
Results: The odds ratio (OR) for ever vs never having had an ocular tonometry test was statistically significant for matched and unmatched analyses for 15 through 3 years prior to disease onset, using both control self-responses and control surrogates: ORs were ∞ and 19.4 with 1-sided P-values <0.0001 and 0.003 and ORs=∞ and 11.1 with 1-sided P-values <0.003 and 0.02, respectively. ORs increased as the number of tonometry tests increased during this age period: trend test, 2-sided P-value < 0.0001. For ≥5 vs <5 tonometry tests, the OR was 5.8 (unmatched) and 3.7 (matched), 2-sided P-value<0.00005. Respondents generally could not specify the type of tonometry. There was no indication of increased tonometry testing among cases within 2 years of disease onset.
Conclusions: The a priori hypothesis was supported. Contact tonometry, preferred by ophthalmologists, may be capable of transmitting sCJD. Consideration should be given to using disposable instrument covers after each use. The use the disposable covers or non-contact tonometry is preferable in the absence of effective disinfectant processes at this time.
Keywords: Sporadic creutzfeldt-Jakob disease (sCJD), prion diseases, intraocular pressure(IOP)test, risk factors, iatrogenic transmission, eyes, ophthalmology, case-control study, neuroepidemiology