Discuss the provision of diagnostic virological services to a district general hospital
In assessing the provision of diagnostic virological services to a district general hospital, one must consider the actual needs of the hospital and budgetary and practical considerations.
Needs of the hospital
District general hospitals vary greatly in size, the services provided and in the population they serve. The following questions should be addressed in the assessment of the needs of the hospital;-
1. The size and the type of population that the hospital serves;- eg. whether the population is rural, suburban or inner city. From this, one would have some idea on the actual volume of tests and the type of tests likely to be requested. eg. inner city populations are likely to have a high preponderance of drug addicts and prostitutes and thus a higher prevalence of hepatitis B and HIV.
2. The location of the hospital, especially in relation to the nearest regional or area virus laboratory. The nearest regional or area virus laboratory may vary from a few miles to up a a hundred miles. Obviously, it would probably prove to be easier and cost effective to send most requests for virology testing if the nearest virus laboratory is only a few miles away. On the other hand, if the nearest virus laboratory is a long distance away, the transport costs would be enormous especially in case f urgent specimens which would probably have to be sent by taxi or courier. Obviously in this case, the incentives for setting a comprehensive diagnostic virology service would be greater.
3. Special needs that the hospital may have ;- For
example, does the hospital carry out transplant operations? Does
it have a haemodialysis unit? Does it have a large paediatric and
special care baby unit? Does it offer obstetric services?
Financial and Practical Considerations
This has been made very complicated by the NHS reforms. Regional and area virus laboratories are due to charge district hospitals for each individual investigation requested. The key question here is whether it would cost more or less to provide a diagnostic virological service in the hospital. To this end, one should consider and estimate the costs involved in each individual investigation and compare to what it would cost to send to the nearest regional or area virus laboratory. Another consideration would be that by providing a local diagnostic service, one would be able to charge local general practitioners who use the service, and therefore should help to finance the service.
However, many practical considerations need to be taken into
account. For example, is there spare space in the existing
microbiology laboratory to accommodate the new virology service?
Could existing laboratory technicians in microbiology carry out
the new tests without much need for further training or would new
posts for laboratory technicians trained in virology have to be
created? If the hospital in question is situated in a remote area,
then one could envisage great difficulty in recruiting trained
virology technicians as opposed to a hospital situated in a big
Individual Services to be considered
Bearing in mind needs of the hospital and financial and practical considerations, the microbiologist, in consultation with clinical colleagues should then look at each virological service carefully.
1. Virus Culture - the provision of a tissue culture facility is certainly not a practicable proposition for the vast majority of District General Hospitals. It is very expensive to set up and maintain and requires trained virology technicians. There are also safety consideration involved especially with biohazard group III pathogens. It may be worth considering if there is a large paediatric unit and/or the presence of a large organ transplant unit and that the hospital is a long distance away from a regional or area virus laboratory. If there is a large organ transplant program, there might be great pressure from the clinical staff to provide a diagnostic, in particular a rapid diagnostic service for CMV. In theory, the use of the CMV antigenaemia test on the buffy coats of patients should provide a means of the rapid diagnosis of active CMV infection without resort to tissue culture. However, in practice, the test is very difficult to carry out.
2. Electron Microscopy - the vast expense involved in the setting up and the running of this service most definitely make it an unrealistic proposition for a District General Hospital. It is certainly worthwhile providing a service for diagnosing rotavirus antigen in faeces. It is anticipated that with time, more and more commercial assays would become available for the detection of other diarrhoel virus antigens in faeces.
3. General Serology - complement-fixation tests are carried out by many microbiology laboratories for the diagnosis of bacterial diseases. Therefore, it may be possible simply to add to the existing service. If complement-fixation tests are not already carried, there is little justification in setting up such a service. Serological tests for the diagnosis of EBV and CMV infections should definitely be considered though, as infectious mononucleosis is a very common disease and CMV is a important pathogen in immunocompromized patients.
4. Rubella - the decision of whether to set up a diagnostic service for rubella would probably be based mainly on economic reasons. ie. whether it would be cheaper to carry out antenatal testing locally rather than to send it to the nearest virus laboratory. This would depend greatly on the volume of work anticipated. The easiest screening test to perform ie. latex agglutination, would be preferable to single radial haemolysis. Consideration should also be given to setting up a diagnostic service for acute rubella and parvovirus infections using commercially available IgM assays although it would be highly doubtful that the volume of requests would justify such a service.
5. Hepatitis - testing for HBsAg should definitely be regarded as a top priority. It may be more practical to leave test for other hepatitis B markers eg. core antibody, core IgM and HBsAb to the nearest virus laboratory. The provision of a diagnostic service for hepatitis A, C, and E must depend on the expected volume of requests.
6. HIV - it would probably be desirable to have the facility to test for HIV antibody. Although confirmatory testing and other tests such as testing for HIV viral load and antiviral resistance could be left to the nearest reference virus laboratory.
7. Rapid diagnostic tests - it would be highly desirable to have the facility to examine nasopharyngeal aspirates for RSV and other respiratory viruses such as influenza A and B, parainfluenzaviruses and adenoviruses. Recent advances in molecular biology have put molecular biology techniques such as PCR and LCR within the reach of a district general hospital.
8. On call service - any on call service provided should fit in with existing on call microbiology services. On call services could normally be left to the nearest virology laboratory unless the distance involved is too great. On call services should be restricted to screening potential organ donors and haemodialysis patients, and possibly needle stick injuries which had occurred over the weekend.
Virus Culture 4
Electron Microscopy 4
Rotavirus antigen 1
General Serology 2
Rubella - antenatal screening 2
Rubella - acute infection 3
Hepatitis B - HBsAg 1
other markers 3
Hepatitis A 2
Hepatitis C 3
HIV - screening 2
other markers 3
Nasopharyngeal Aspirates 1
On call service
1 highly desirable
2 should be considered
3 can be considered if circumstances dictate but not likely to be practicable or economical
4 extremely unlikely to be practicable
To conclude, the provision of diagnostic virological services to a district general hospital should be taken on an individual basis based on the needs, expertise, financial resources and facilities available in that hospital.