Epidemiological analysis of corneal donors and patients queuing for keratoplasty

Purpose: To characterize corneal donors and patients on the waiting list for keratoplasty clinically and epidemiologically. Methods: Epidemiological, cross-sectional study with a sample of 1,303 donors and 938 patients on the waiting list were analyzed. Performed in MS State Transplant Center (STC) and the Human Ocular Tissue Bank, from January to June 2019. For the qualitative variables, descriptive analysis was performed. In the quantitative variables, trend and data dispersion measures were analyzed. Results: Of the 2,606 corneas, 31.73% were transplanted, 21.64% of donors were reagents for infectious diseases that contraindicated transplantation, with a higher percentage of reagents in donors aged over 50 years (p <0.001). Keratoconus stood out as the main ocular diagnosis in the frequency distribution. The average age found for patients in the waiting line was 49.05 years. Regarding the average waiting time to perform the transplant, it was 108.46 days for elective transplants and 11.0 days for emergency transplants. Conclusion: More than 40% of the tissues taken from donors were discarded, with emphasis on epithelial defects and reagent serologies. Keratoconus was the main indication of patients queuing for keratoplasty.


INTRODUCTION
Corneal diseases represent one of the main causes of reversible blindness in the world and keratoplasty, the most performed transplant in the world, consists of surgical and therapeutic treatment to restore visual function and improve the quality of life of patients on waiting lists through free tissue flaps (CRUZ et al., 2017).
Corneal blindness represents the fourth leading cause of blindness in the world.
Programs to prevent injuries and diseases that affect the corneas have been implemented globally to avoid complications that lead to more intensive treatments such as keratoplasty. Access to transplantation is still hampered by the scarcity of corneal tissues available for lack of donors, however, even in developed countries (PINEDA, 2020;WHO, 2019).
Brazil has the largest public transplant system in the world, serving approximately 96% of the demand of the Unified Health System (UHS), through its National Transplant System (NTS). The NTS is responsible for the process of capturing and distributing the donated organs and tissues nationally, as well as for the management of waiting lists (BRAZIL, 2019).
The year 2019 showed a 1% increase in the rate of corneal transplants in Brazil when compared to the previous year, however, it was not possible to reach the planned goal, which made it difficult to reach the "zero list" of patients waiting for the procedure. This situation reflects the insufficient notification of potential tissue donors, effective donors and brain death in the country.
In this context, nursing plays a crucial role, since the Federal Council of Nursing regulated by Resolution no. 292/2004 the role of nurses throughout the process of donation and transplantation, and it is up to enforce the term of tissue donation, in addition to carrying out the enucleation of the eyeballs, as long as they are enabled, with follow-up, supervision and quality assurance of the process. Thus, nursing professionals must be aware of the conditions of donors and the waiting demand for keratoplasties in all authorized services (COFEN, 2004).
Thus, measures are necessary in Brazil to end this stagnation in all spheres involved in the transplantation process (ABTO, 2019). This study aims to characterize corneal donors and patients on the waiting list for keratoplasty clinically and epidemiologically in the state of MS, Brazil.

METHOD
This is a quantitative, cross-sectional and descriptive study, based on secondary data collected from the MS State Transplant Center (STC) and the Human Ocular Tissue Bank, from January to June 2019.
A census study was carried out, whose data were collected from information in medical records and record sheets. A pilot study was initially carried out in order to make the collection instrument more complete and accurate, including the medical records used in that phase in the final sample. An adapted instrument was used, based on a previous study (CRUZ, 2015), with prior authorization, referring to donors and patients on the waiting list registered in the STC, for a period of 5 years, from January 2014 to December 2018.
This time frame of analysis was due to the objective of conducting a quantitatively robust study, with a sample above the statistically necessary for analysis, carried out with a census sample and also capable of correcting a punctual change in the absolute number of corneal transplant procedures performed pmp in 2014, which presented a decrease when compared to previous years, with an increase in this number in the following years. During this period, data were obtained from corneal donors and patients on the waiting list for keratoplasties.
The data collected related to the donors and the patients on the waiting list during the data collection period. Both the patients actually on the waiting list and those who had already been transplanted on within the timeframe were studied. This inclusion criterion aimed to analyze in a longer time interval, which was the time expected to perform the intervention, and the characterization of the subjects.
Thus, the total population consisted of 1,303 donors and 938 patients on the waiting list. Of these, 796 had already undergone keratoplasty and 142 were awaiting the procedure during the data collection period.
The medical records of all those who met the pre-established criteria, of both sexes, without age limitation, regardless of the clinical condition indicating for registration in the NTS, were included, as there was logistical and operational feasibility to justify the population census. Patients whose medical records were not located or whose information was illegible, essential to meet the proposed objectives according to the variables studied, were excluded.
The database was built in a spreadsheet using Microsoft Excel® version 2017.
For the data analysis, construction of descriptive tables and application of statistical tests, the free statistical software R, version 3.0.0 was used. For the qualitative variables, the descriptive analysis was carried out through absolute and relative frequency distribution. For the quantitative variables evaluated, of trend and data dispersion measures were analyzed. When comparing the general characteristics of donors and patients on the waiting list with the clinical data, the Chi-square and Fisher's exact tests were applied. For all tests, the significance level adopted was 5%. The variables investigated concerning the donors were: sex, age group, color, place of residence, size of the corneal button, cause of death, donated cornea, serological status, abnormalities; and concerning the patients on the waiting list: gender, age group, eye diagnosis, transplanted eye, surgical purpose, type of surgery and transplantation.

RESULTS
The profile of the corneal donor in the state did not differ from that found in other regions/states of Brazil and other countries in the world, as well as their causes of death. During the study period, 1,303 corneal donors were registered in the state of MS, whose sociodemographic characteristics are shown in Table 1 below.   Statistically significant differences were found when analyzing the variables "eye diagnosis" crossed with the characterization variables such as gender, age group, surgical purpose and type of surgery (Table 4). As for race, mulatto (51.96%) and white (43.44%) patients were found more frequently in the study, followed by black (4.45%) and yellow (0.15%) individuals. The In a study in Paraná, positive serology was the reason for discarding in 49.6%, against 68% in a study in the Federal District. The significant statistical relationship found between donors over 50 years of age and seropositivity for contagious infectious diseases that contraindicate transplantation is justified by the increase in life expectancy coupled with the advance in health technologies that prolonged sexual life in the elderly.
Another justification is that the population in general and even health professionals still treat sexuality in old age as a taboo (VICTER et al., 2019;FREITAS et al., 2019;BRAZIL, 2015;BASTOS et al., 2018).  The level of education and knowledge of the patient in relation to the procedure that will be submitted are as important as the surgical act itself, so the performance of the nursing team becomes essential for monitoring the client who will perform the corneal transplant throughout the process from preoperative to hospital discharge. Thus, the transplant becomes a safe process with adequate recovery for the transplanted. The When considering the data obtained from this study, noted that patients queuing for keratoplasty maintained a significant number throughout the investigated period, which refers to a demand not met by the corneal transplant system, due to an insufficient number of corneas suitable for the procedure. It is noteworthy that almost half of the corneas collected after donation were discarded, due to clinical and laboratory screening criteria. This way, if the losses were smaller, the lines would be reduced or even eliminated.
Reactive serologies and the structural and functional conditions of the captured corneas were the limiting factors, which indicates the need to improve the screening process of potential donors for more effective captures, with the need for more studies to assess the weight of these factors to target services of corneal transplants.
This study allows to identify factors related to the clinical and epidemiological characterization of donors and patients on waiting lists and to cover variables with a view to expanding the knowledge about this process, thus improving the corneal capture system in the state, as the discards of this ocular tissue present expressive numbers when compared to other countries. In addition, family refusal is still a limiting factor in the uptake of ocular tissue, and thus needs further research with a view to sustaining government strategies to reduce the waiting list to zero.
One limitation in this study is the absence of some donor data due to incorrect or nonexistent completion, so that not all information could be used for description and analysis. This corresponds to a very small part of the research sample though. Thus, the total number of subjects analyzed in the study reduced the possible bias deriving from these losses.