Prevalence and causes of needlestick injuries among dental care providers: A systematic review and meta-analysis

Background The objective of this systematic review and meta-analysis was to identify the prevalence and causes of NeedleStick Injuries (NSI) among dental care providers. Methods Data collection was carried out through searching the following key words: needlestick injuries, injuries, prevalence, occurrence, etiology, risk factors. The following databases were searched: Google Scholar, PubMed, Scopus, MagIran, Iranian Scientic Information Database (SID) and IranMedex. Moreover, some relevant journals and websites were searched manually and the reference lists of the selected articles were checked. In the nal stage of the literature review, we searched the gray literature and contacted the experts whenever needed. Results From 765 articles reviewed, 31 cases were included in the study. In total, the needlestick injury history of 6,737 people (4,402 dentists, 1,000 Dental Health Care Workers (DHCWs) and 1,335 students) had been reported. The overall prevalence of NSI was 48% at an average of 11.1 months. About 69% of NSI cases were not reported. About 79% of the different groups of DHCWs had been vaccinated for the hepatitis B virus (HBV). The most important factors affecting the occurrence of NSI were categorized into two groups of individual factors (lapse in concentration, stress, lack of adequate trainings, and not using safety precautions) and patient-related factors (unexpected patient movements, anxious and uncooperative patients). The occurrence of NSI during treatment procedure (40.1 mean propotion), doing injections (34.2 mean propotion) and recapping (30 mean propotion) were the most important procedures causing NSI among dentists. Conclusion Results of the study show thatprevalence of NSI among DHCWs is high, incidence report of NSI is low and vaccination rate for prevention of bloodborne diseases is inadequate. In this regard it’s recommended to design and implemented comprehensive preventive measures to reduction of NSI prevalence, increase reporting of NSI and vaccination rate


Background
The injury caused by needlestick and sharp objects while working in health care environments is one of the major health threats among the health care providers. This means that NSI and injuries caused by sharp objects such as blood-contaminated syringes and needles infected by patients' body uids can seriously threaten the health of health care workers [1][2][3]. The most important complications cuased by these injuries are HIV, hepatitis B and hepatitis C virus infection [4][5][6]. According to the results of a study in the US, a total of 894 people suffered from these kinds of injuries in a 6-year period among which 30 cases had been infected with hepatitis C virus, 6 cases with hepatitis B virus and 3 cases with HIV [7]. Needless to say, these injuries dramatically increase health care costs [8,9].
In the conducted studies, the prevalence of NSI has been reported very differently [10][11][12][13][14][15][16][17][18]. In England's National Health Service (NHS), the injuries caused by needlestick (with 17%) are considered to be the second most harmful medical events [19]. Negligence and carelessness of the personnel, not using safety precautions and lack of su cient information and knowledge on the principles of prevention and protection against these types of injuries were also reported as the most important factors of needlestick incidence [20][21][22][23][24][25].
Dentists are a group of health care providers who are at a high risk for NSI [26][27][28], in a way that every dentist experience needlestick at least once during his/her professional career [29]. Several studies have shown a high NSI prevalence among dentists [30][31][32].
Despite many studies have been conducted so far on the prevalence and causes of needlestick among dentists in different parts of the world, there is a need to summarize the results of these studies and provide a clear view for planning, decision making and effective interventions. Also there is some systematic review studies in this topic [33][34][35], but thses review studies not provide a compherhencive view about deferent aspects in this eara such as incidence report of NSI or vaccination rate. This systematic review and meta-analysis aims at evaluating the prevalence of NSI in different countries and investigating related factors among dentists.

Methods
This systematic review and meta-analysis was conducted in accordance with the systematic review approach adopted from the book entitle "A Systematic Review to Support Evidence-Based Medicine" in 2017 [36].The study was in accordance with the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement (PRISMA) (Supplementary 1) [37].
Inclusion/exclusion criteria Eligibility criteria consisted of: rst, cross-sectional studies on the prevalence and causes of needlestick among DHCWs, and second, the articles published in Persian and English languages. All the articles published before 1st January 2000, conference presentations, case reports, Interventional and qualitative studies were excluded from the study.

Information Sources
The required data were collected through the keywords related to the search strategy as follows: needlestick injuries, percutaneous injuries, epidemiology, prevalence, occurrence, etiology, risk factors. 6 databases were screened: Google Scholar, PubMed, Scopus, MagIran, Iranian Scienti c Information Database (SID) and IranMedex. Moreover, some relevant journals and websites were searched manually and the reference lists of the selected articles were checked. In the nal stage of the literature review, we searched the gray literature and contacted the experts whenever needed.

Review Process
In the rst phase of the review process, an extraction table was designed. The table included the following items: rst author's name, publication year, country, sample size, participants, NSI prevalence percentage, time period (month), unreported NSI, vaccination percentage for Hepatitis B virus (HBV), the NSI causes, and the most important factors causing NSI. Validity of the tabulated data was evaluated by experts, and a pilot study (with 5 articles) was conducted for further improvement of the data extraction. Two experienced and knowledgeable authors were responsible for extracting the data independently.
In rst phase of article selection, articles with non-relevant titles were excluded. In the second phase, the abstracts and full texts of the retrieved articles were reviewed to include those articles matching the inclusion criteria. Reference management (Endnote X5) software was used for organizing and assessing the titles and abstracts, as well as for identifying the duplicates. Microsoft Excel 2010 software was used to draw the graphs.

Quality Assessment
Two reviewers evaluated the articles according to the checklist of Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) [38]. Controversial cases were referred to a third author.

Data Analysis
To estimate the overall NSI prevalence, the Comprehensive Meta-Analysis (CMA: 2) (Englewood, NJ, USA) software was used. In order to report the results, forest plot was employed. In the forest plot the size of each square shows the sample size and the lines on each side of the square show the Con dence Interval (CI). NSI prevalence was calculated using xed effects model with 95% con dence interval. To measure the heterogeneity of studies, Q and I 2 indicators were used. I 2 index higher than 50% was suggested as indicative of substantial articles heterogeneity.

Results
Out of 765 articles retrieved from databases and other sources, 345 cases were removed due to duplicates. In title and abstract screening, 372 other papers were excluded from the study. In the full-text review, 17 cases were also excluded, and 31 articles were nally included ( Figure 1).
The characteristics of the articles included in the study are presented in Table 1. Out of 31 articles reviewed, 22 studies had been conducted in low/middle-income countries. Taking the reporting method of the articles into account, the participants in this study were divided into three groups of dentists (specialist, general), dental students and DHCWs (including dentists, dental students, dental nurses and others). In total, the NSI information of 6,737 people (4,402 dentists, 1,000 DHCWs and 1,335 students) had been reported. In addition, in eight articles the time periods had not been mentioned; in one article the time period was too long (5 years); and in another study the period was very short (1 week). Hence, these 10 articles were not included in the analysis of NSI prevalence.
The prevalence of NSI among DHCWs (dentists, students, dental nurses and others) with a 95% con dence interval based on the income of the countries (high-income countries, low/middle-income countries) and the information presented by the World Bank [39] is shown in Figure 2.
The average prevalence percentage of NSI among DHCWs was estimated 48% during 11.1 months, 37% in high-income and 52% in low and middle income countries respectively. (See Table 2 for more details). The prevalence of NSI among dentists, dental students and DHCWs (dentists, students, dental nurses and others) was 43%, 56%, and 33% respectively ( Figure 3 -more detailed information in Figure 2).
The results also revealed that about 69% of NSI cases among different groups of DHCWs were not reported. This rate is 67% in high-income countries and 69% in low/middle-income countries (Figure 4 -More detailed information in Table 2). Furthermore, this rate is 82% among dentists, about 84% among DHCW and 71% among students ( Figure 5 -more detailed information in Table 2).
The results revealed that about 79% of the different groups of DHCWs had been vaccinated for hepatitis B. This rate is 88% in high-income countries and 71% in low/middle-income countries (Figure 6 -More detailed information in Table 2). In addition, this rate is 82% among dentists, about 84% among DHCWs and 71% among students (Figure 7 -more detailed information in Table 2).
Only three studies had mentioned the factors affecting the occurrence of NSI [29,40,41]. Based on the analysis of the results of these three studies, the most important factors affecting the occurrence of NSI were categorized into two groups of individual factors (lapse in concentration, stress, lack of adequate training, and not using safety precautions) and patient-related factors (unexpected patient movements, anxious and uncooperative patients). The occurrence of NSI during treatment procedure (40.1 mean proportion), doing injections (34.2 mean proportion) and recapping (30 mean proportion) were the most important procedures causing NSI among dentists.

Discussion
From 765 articles reviewed, 31 cases were included in the study. In total, the needlestick information of 6,737 people (4,402 dentists, 1,000 dental health care workers (DHCWs) and 1,335 students) had been reported. The overall prevalence of NSI was 48% at an average of 11.1 months. About 69% of NSI cases were not reported. About 79% of the different groups of DHCWs had injected the hepatitis B virus vaccines. The most important factors affecting the occurrence of NSI were classi ed into two groups of individual factors (lapse in concentration, stress, lack of adequate trainings, and not using safety precautions) and patient-related factors (unexpected patient movements, anxious and uncooperative patients). The occurrence of NSI during the treatment procedure, doing injections and recapping were the most important procedures causing NSI among dentists.
The overall prevalence percentage of NSI among DHCWs was 48% at an average period of 11.1 months, 37% in high-income countries and 52% in low/middle income ones respectively. Studies evaluating the prevalence percentage of NSI among other health care providers showed lower rate than that among DHCWs [42][43][44][45]. Given the high risk of different viral infections such as Human Immunode ciency Virus (HIV), hepatitis B, hepatitis C and other types of bloodborne infections through blood products in NSI cases, this rate of NSI prevalence is critical [30,32,40,[46][47][48][49][50].
The concern increases realizing that according to the results of the studies, about 69% of NSI cases had not been reported by different groups of DHCWs, and about 21% of the workers had not been vaccinated. The results also showed that the prevalence of NSI in low and middleincome countries is signi cantly higher than high-income countries. Moreover, due to high number of unreported NSI cases in low and middle income countries, the differences between these two countries are expected to be higher than those reported in this study. The possible reasons include: provided with better educational and training courses, using more safety precautions, more appropriate environmente and working facilities in high-income countries. Also, the prevalence percentage of NSI among dental students was higher than that of dentists, which can be attributed to the lack of adequate skills and experience .
The results showed that about 69% of NSI cases were not reported by different groups of DHCWs. This rate is 67% in high-income countries and 69% in low and middle-income countries. Also, this rate is 82% among dentists, 84% among DHCWs and 71% among students. The main factors for failure to report NSI cases include: being too busy (especially dentists), lack of awareness, fear of testing and cross-infection, problems with reporting system and the belief that the exposure was not signi cant [51]. The rate of unreported NSI cases among dentists was higher than that of the students, which can be attributed to the heavy workload of dentists as well as the students' belief that the exposure is signi cant. The most important measures are: implementation of an appropriate and e cient system for reporting and tracking of injuries, training care providers on the risks and consequences of failure to report (and following up) the injury cases, providing incentives and appropriate cultural settings.
The results showed that about 79% of different groups of DHCWs vaccinated for hepatitis B virus. The results of the study conducted by Pruss-Ustun and colleagues showed that, in 2000, about 66,000 cases of NSI-related hepatitis B infections had been recorded among health care providers all around the world [52]. Other studies also highlighted the high prevalence of hepatitis B caused by NSI [53][54][55][56][57][58][59]. Considering the high prevalence of NSI and the risk of hepatitis B among dentists, it is essential to pay a special attention to the NSI prevention guidelines and a full coverage for hepatitis B virus vaccination.
Out of 31 articles which were included in the study, only three articles had mentioned the factors affecting the occurrence of NSI. Since a clear understanding of the effective factors related to NSI incidence can play an effective role in planning preventive measures, it is suggested to be considered in future studies. Lapses in concentration, stress, lack of adequate training and not taking safety precautions were the most important factors affecting the NSI incidence. In this regard, many studies have shown that dentists do not take safety precautions in a su cient manner [60, 61]. The lack of adequate trainings is also an important factor in NSI incidence. To solve this problem, it is recommended that students and dentists take appropriate courses on the Moulage training programs before starting any new treatment procedure.
It is documented that most NSI occurred while injecting and recapping used needles among dentists. In this regard, the use of safety devices can have a signi cant effect on reducing the occurrence of NSI among dentists [32,62,63]. The results of the study by Zakrzewska and colleagues in England showed that the use of safety syringes reduces the NSI incidence from 11.8 to 0 per 1 million hours of work per year [64]. Therefore, it is necessary to take giant leaps to reduce the occurrence of NSI through such measures as the mass production and optimization of safety syringes, reducing their costs, introduce and make the dentists aware of utilizing them.
The main limitation of the present study is that our search for articles was merely in English and Persian languages and all other languages were ignored. Also, due to the fact that only three articles had mentioned the causes of the NSI, further analysis was not possible for this issue.

Conclusion
Results of this study show that prevalence of NSI among DHCWs is high (48% at an average of 11.1 months), incidence report of NSI is low (about 69%) and vaccination rate (about 79%) for prevention of bloodborne diseases is inadequate. In this regard it's recommended to design and implemented comprehensive preventive measures to reduction of NSI prevalence, increase reporting of NSI and vaccination rate. These measures can be cover the use safety syringes, take safety precautions during work, design an e cient NSI reporting system, administer fulldoses of vaccines, follow the standards and guidelines and increase the knowledge and awareness of the staff. The prevalence of NSI among DHCWs (dentists, students, dental nurses and others) with a 95% con dence interval based on the income of the countries (based on the xed model) Figure 6 Total injection rate of hepatitis B virus (HBV) vaccines by different groups of DHCWs based on income of the countries with 95% con dence interval (based on xed model).