Evaluarea serologică a protecției față de hepatita B în rândul personalului medical

  Serological evaluation of the protection against hepatitis B infection among healthcare personnel

First published: 15 februarie 2017

Editorial Group: MEDICHUB MEDIA

Abstract

Background. The medical staff is a recognized risk group for the professional exposure to hepatitis B virus, an infection against which it is necessary to ensure protective measures. The aim of the study was to evaluate the serological protection against hepatitis B virus infection of the healthcare personnel after the introduction of the vaccination into practice.    
Methods. A convenient sample among medical staff was identified on the basis of the existence in the surveillance medical records of the serological determination of the level of antibodies for surface antigen of hepatitis B virus. The blood sampling was made in practical conditions and for antibodies level was used the immunoenzimatic test. The database was made in Excel and the descriptive and analytical statistics were made in Epi Info 7. 
Results. Among the 96 medical personnel staff included in the sample, 83.3% of them were vaccinated with a complete scheme. Protective antibody level was present in 84.38% (CI 95%: 75.54-90.98) of persons, in 88.75% (CI 95%: 81.9-95.25) of vaccinated persons and in 62.5% (CI 95%: 37.64-83.17) of unvaccinated personnel, with a risk ratio of 1.42 (CI 95%: 0.93-2.09). From an acute episode of hepatitis suffered 11.5% (CI 95%: 6.17-19.04%) of persons and 2.08% (CI 95%: 0.35-6.71) of the medical staff were persistently infected or with chronic consequences.  
Conclusions. The serological test for the evaluation of protection after vaccination against hepatitis B virus infection must be done carefully in a heterogenic population with vaccinated persons, but also with those who went through natural infection and with persistent infection.  

 

Keywords
hepatitis B, vaccination, serological evaluation

Rezumat

Introducere: Personalul medical este recunoscut a fi un grup la risc pentru expunerea  profesională la infecția cu virusul hepatitei B, infecție față de care este necesară asigurarea măsurilor de protecție. Scopul acestui studiu a fost evaluarea serologică a protecției personalului medical față de infecția cu virusul hepatitei B, după introducerea vaccinării în practică.   
Metodă: A fost selectat un eșantion convenabil, pe baza existenței în evidențele medicale pentru supraveghere a rezultatului determinărilor serologice a nivelului anticorpilor  față de antigenul de suprafață al virusului hepatitei B. Probele de sânge au fost recoltate în condiții uzuale, iar nivelul anticorpilor a fost măsurat folosind teste imunoenzimatice. Baza de date a fost făcută în Excel, iar statistica descriptivă și analitică a fost realizată în Epi Info 7.     
Rezultate: Printre cele 96 de persoane incluse în eșantion, 83,3% au fost vaccinate cu schema completă. Nivelurile protectoare de anticorpi au fost prezente la 84,38% (CI 95%: 75,54-90,98) dintre persoanele testate, la 88,75% (CI 95%: 81,9-95,25) dintre cei vaccinați în antecedente și la 62,5% (CI 95%: 37,64-83,17) dintre cei nevaccinați, iar riscul relativ a fost de 1,42 (CI 95%: 0,93-2,09). Un episod acut de hepatită au avut în antecedente 11,5% (CI 95%: 6,17-19,04) dintre persoanele incluse în eșantion și 2,08% (CI 95%: 0,35-6,71) prezentau infecție  persistentă sau o hepatită cronică. 
Concluzii: Testarea serologică pentru evaluarea protecției după vaccinarea anti-hepatită B trebuie efectuată cu prudență într-o populație heterogenă, incluzând persoane vaccinate, trecute prin infecția naturală sau prezentând consecințe cronice ale infecției. 

Introduction

Healthcare personnel is a recognized category to be at risk for infection with hepatitis B virus (HBV) after professional exposure(1,2). Beside the prevention through the personal protective equipment for the contact with blood and biological fluids, the hepatitis B vaccination confers a long term specific protection(3-5). This immune protection is due to a humoral response with antibodies against the determinant a, from the complex structure of the surface antigen of hepatitis B virus (AgHBs)(3,6,7). Serological tests for identification of the level of the antibodies against Ag HBs (HBs Ab) are used in population surveys to study the herd immunity and collecting data necessary for vaccination recommendations(8). The individual determination of the immune response after hepatitis B vaccination isn’t recommended because the vaccine efficacy is high, after vaccination the immune memory is installed and the incubation period of hepatitis B is long enough, permitting the installation of the secondary immune response and protecting the person against hepatitis B infection after an accidental contact(3,4,5,7). Particularly, the importance of knowing the individual serological protection is high for persons at high risk for HBV infection like the medical personnel, who is in consistent contact with blood, infants of infected mothers or immunodeficient patients(3,5).

The hepatitis B vaccination program in Romania started in 1995, with newborns and the medical staff, continued with teenagers in the last grade of high school (or eighteen-year-old teenagers) and the nine-year-old children. In the present, because all other age groups up to those of adults are vaccinated, the vaccination programme continues with newborns.

The objective of this paper is to evaluate the protection for hepatitis B infection of the healthcare staff using the serological determination, after the introduction of the hepatitis B vaccination in the generalized vaccination programs.

Methods

In order to evaluate the protection against HBV infection, we identified from the existing medical records for surveillance the personal staff from the Infectious Diseases University Hospital Cluj-Napoca who had the recommendation for the serological determination of the level of HBs Ab necessary to the employment, for periodic medical examination or have asked it themselves. Among these people, it was selected a convenient sample, the inclusion criteria, beside the HBs Ab result, being the identification of data regarding the age, gender, professional grade, vaccine and pathological antecedents regarding acute hepatitis.    

 

Tabel 2 infectio



The blood samples for serological tests were taken in the hospital’s rooms for biological sampling, in practical conditions. A quantity of 5 ml of blood was drowned by venipuncture from the median cubital vein, localized within the cubital fossa anterior to the elbow and then transported to the laboratory. In the lab, all blood samples have been decanted, centrifuged for 2 minutes at 5,000 rotations/ minute and stored frozen at -200C until performing the immunoenzimatic test, using the kits ETI-AB-AUK-3 DiaSorin. The enzymatic test was characterised by a sensitivity of 99.6% and a specificity of 99.8%. The cutoff value of the HBs Ab protective level was considered 10 mUI/ml serum.

 

Figure 1
Figure 1. The distribution of vaccinated medical staff regarding the number of administered vaccine doses.  In the graph are labelled the number of doses and in percent the persons vaccinated with the specified number of vaccine doses


The necessary data after identification, validation and registration on paper were recorded in an electronic database made in Excel for Windows 2007. The descriptive statistics included the percentage, confidence intervals of 95% of values, the test for significance and the analytical one, which was based on risk ratio of protection frequency. The statistics for the selected variables was performed in Excel and Epi Info 7.

 

  • Figure 2 - Infectio
    Figure 2. The proportion of protected and unprotected medical staff from the sample, evaluated through the serological level of antibodies. In the graph are represented the protected persons in the entire sample and divided regarding the professional level and the vaccination antecedents.
  • Figure 3 - Infectio
    Figure 3. The correlation between the age and serological protection to B hepatitis.  It is represented the proportion of the protected persons from the analyzed sample and the correlation equation. The age groups are: 1=20-29 years; 2=30-39 years; 3=40-49 years and 4=50-59 years old



Results

A total number of 96 persons, who presented all the necessary data, were included in the study sample. In this sample, the serological determinations were made in the period 2002-2003, after the introduction of the mandatory hepatitis B vaccination for the non-immune medical personnel. In the identified sample, 90.63% (CI 95%: 82.95-95.62) were female, 95.83% (CI 95%: 89.67-98.85) were persons from urban area and belonging especially to the age group of 30-39 years (Table 1). Regarding the professional level, 32.29% were medical doctors and 67.71% were nurses.

In their antecedents, 11.5% (CI 95%: 6.17-19.04) of persons had an episode of acute hepatitis, without knowing certainty its etiology (A, B or C) and 2.08% (CI 95%: 0.35-6.71) of the staff has currently chronic hepatitis or persistent infection with HBV. The vaccination was done for 83.3% of medical staff from the sample, with at least 3 vaccine doses and 7.5% received 4 doses, 1.25% received 5 doses and 3,75% received 6 doses (Figure 1).

A protective antibody level was present in 84,38% (CI 95%: 75.54-90.98) of the analyzed persons, without significant difference (p>0.05) between medical doctors (83.87%; CI 95%: 67.81-93.84) and nurses (84.62%; CI 95%: 74.29-91.91) (Figure 2). In the descriptive evaluation, we found significant differences (p<0.05) between the serological protection of the vaccinated group, who had protective levels in 88.75% (CI 95%: 81.9-95.25) of the persons, and the unvaccinated group, who had serological protection in 62.5% (CI 95%: 37.64-83.17) of the persons. In the analytical analysis, the risk ratio was 1.42 (CI 95%: 0.93-2.09) and didn’t suggest significance. Among vaccinated persons with a 3-dose scheme, 90% (CI 95%: 81.22-95.52) of them were protected, the persons vaccinated with more than 3 doses scheme were protected in 80% (CI 95%: 49.05-96.5) of cases and the difference was statistically significant (t=0.02984), but with a risk ratio of 1.12 and CI 95% (0.81-1.54).

In relation with age evolution, analyzed through ten-year age groups, the serological protection decreased slightly and the correlation coefficient was 14.9%, with a p value of 0.0003 (Figure 3).

Discussions

The particular demographic characteristics of the sample used in this serological B hepatitis protection assessment reflect the structure of the existing professional population active in the healthcare sector. In the last decades, the main characteristic of the demographic medical staff population is the increasing number of women working in this field.

A very similar HBV protection among different categories of medical staff with different responsibilities reflects the effectiveness of protection using the existing methods in the practical activity. Also, even not a significant difference, but with a high level of protection among nurses, can reflect the elevated transmission of HBV and a strong immune response after going through the natural infection.

In our sample, the protective levels were the consequences of vaccination, but also of a HBV infection, difference that can’t be made through serological HBs Ab identification. Reversely, the absence of protection in our sample may reflect the inefficiency of vaccination even with more than 3 doses, avoidance of the infection until the date of the serological test or the presence of the persistent HBV infection or his consequences. In this regard, it’s one more time obviously that the increase of the number of hepatitis B vaccine doses, over the complete scheme, will not improve the protection(9,10,11). For these particular cases, that did not respond to hepatitis B vaccination, searching for infection markers it’s one important option.

One important difficulty in the interpretation of the presence and level of HBs Ab was the lack of information about the etiology of the hepatitis acute episode in the staff antecedents. In that period, in our practical diagnosis activity there were used only a few markers for knowing the type of the acute episode of hepatitis.

The significance of the decreasing serological protection level with age elevation can be relevant in vaccination recommendations(8,12). On the other hand, the assessment process needs to take into account the other possibilities of the presence of an immune response in adult persons, beside the vaccination(13,14,15).

In the present study we could not do the assessment of the protection by gender, because of the male staff number, who was very small (only 9 persons), and the division with other characteristics would had narrowed to much the strata for analysis.

Knowing better the different aspects about hepatitis B protection (especially on using objective evaluation methods) will properly help to elaborate appropriate recommendation for this specific protection against an occupational hazard from the medical environment.  

Conclusions

The results from the analyzed medical staff sample, regarding their serological protection against HBV infection, allow us to say that the demographic particularities in term of gender, domicile area and age reflect the component of the healthcare personnel existent in the health care system. The serological protection is the consequence of the vaccination and also of the natural infection. Vaccine doses number elevation did not improve the serological protection and the search for persistent HBV infection is recommended. The significance of the results of HBs Ab identification must be carefully interpreted, especially for making recommendations concerning the vaccination program. Further evaluations are needed for improving the knowledge about the medical staff HBV infection protection in the transition from a heterogenic protection after natural infection or vaccination, to an almost uniform vaccinated population.

 

Acknowledgements: The authors wish to thank to the nurses who helped them in the collectioning of blood samples, and to the team of the laboratory who performed the serological tests.

Conflict of interests: The authors declare no conflict of interests. We didn’t have any financial support for this work.

Bibliografie

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