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Needlestick and risk in Taiwan

 

Clinical bottom line

The estimate in Tainwan is that about 1,000 healthcare workers out of 100,000 suffer seroconversion with HBV and HCV through needlesicks with hollow bore needles annually. This high figure reflects a high patient prevalence of HBV and HCV.


Reference

J Shiao et al. Estimation of the risk of bl pathogens to health care workers after a needlestick injury in Taiwan. American Journal of Infection Control 2002 30: 15-20.

Study

This study set out to estimate the annual risk for contracting hepatitis B, hepatitis C and HIV after a needlestick injury with a used narrow bore needle. It did this using several methods.

The incidence of needlestick injuries in workers in 16 randomly-selected hospitals of the 132 in Taiwan, stratified by size. There were 10,500 healthcare workers, and 83% completed a questionnaire about needlestick injuries and the type of device in the previous 12 months.

HBV, HCV and HIV antibody prevalence in patients using residual sera of 1805 collected on four days in separate quarters of the year. This was a 10% sample of the patients admitted on each of the four days. Half the diagnoses were for cancer, circulatory problems, poisoning and injury, and diseases of the respiratory system. This was somewhat different than for the whole hospital population.

Seroconversion rates were taken from the literature.

Results

Needlestick

Needlestick injuries occurred in 7,750 workers (87%) during the previous 12 months. Of these, 64% involved a hollow bore needle, and in 3% the cases was unknown. A figure of 67% hollow bore needles was used as the basis for calculations on susceptibility to pathogen transfer.

For each class of worker, figures from the questionnaire were used to calculate the number of contamination exposures a year, which ranged from 0.7 per year for nurses to 0.3 per year for support personnel.

Not all workers were protected against HBV, and 28% had neither natural protection nor had been vaccinated.

Patient prevalence

Antibodies to HBV were present in sera of 17% of patients, HCV in 13% and HIV in 0.8%.

Risk of exposure to bloodborne pathogens

The yearly risk of exposure to bloodborne pathogens was estimated by multiplying the number of contamination exposures per year by the prevalence of each pathogen by the proportion of workers susceptible to the particular pathogen (28% for HBV and 100% for HCV and HIV). The results for each group of workers for each pathogen is shown in Table 1.

Table 1: Annual individual risk of exposure to bloodborne pathogens

 

Annual rate of exposure

Category

Annual exposures

HBV

HCV

HIV

All workers

0.6

0.028

0.076

0.005

Nurses

0.7

0.027

0.089

0.006

Physicians

0.4

0.015

0.051

0.003

Technicians

0.4

0.023

0.051

0.003

Support staff

0.3

0.028

0.038

0.002

 

Risk of seroconversion

The literature rates of seroconversion were taken as 10-30% for HBV, 1-10% for HCV and 0.1-0.3% for HIV.

Annual number of seroconversions in Taiwan

This was estimated for the entire Taiwanese healthcare system by taking the annual exposure rates for an individual risks from Table 1, and multiplying by the seroconversion rate and the total number of employees in that category. The results are shown in Table 2.

Table 2: Annual number of seroconversions in Taiwanese healthcare system

Annual number of seroconversions

Category

Total employed

HBV

HCV

HIV

All workers

110,000

300-900

330-840

<1-2

Nurses

66,900

180-540

230-600

<1-1

Physicians

17,710

30-80

40-90

<1

Technicians

16,390

40-110

30-80

<1

Support staff

7,810

20-25

10-30

<1

Comment

This is a detailed paper that shows good methods. A weakness is that the patients whose seroprevalence for pathogens was tested was somewhat different from the hospital population as a whole, but probably not sufficiently so to make any real difference. The number of needlestick injuries each year also seems high by comparison with other studies, but was based on a large sample with high participation by comparison to other surveys.

The lesson is that while individual risk is low, the risk for the healthcare worker population is significant. If each of the needlestick injuries was reported, it would place a high burden on occupational health departments and laboratories for counselling, prophylaxis and testing. That in 110,000 workers about 1,000 each year have occupational infection through injury from a hollow bore needle. Extrapolation to the NHS would suggest 10,000 such instances.

That, though is unlikely. This study demonstrates the methods used, and also the sensitivities involved. For instance, lower needlestick injury rates, lower prevalence of infection in the hospital population, and higher HBV vaccination rates would all lower the number of occupational seroconversions.

The most important is likely to be the prevalence of virus in the population. One UK study demonstrated prevalence of HBV of under 1% in source patients involved in needlestick injuries in the UK, compared to 17% in Taiwan. Population prevalence was also highlighted in French study of the lifetime risk of seroconversion.