Are point-of-care (POC) virological tests what is needed?

Point-of-care (POC) tests are becoming more available, although the way in which they should be used is currently undecided. Any 'laboratory'-based diagnosis of respiratory infections has three components: the specimen taken, the test used, and the interpretation of the results. Each of these components needs to be carefully addressed when using POC tests for the diagnosis of respiratory tract infections. Given the enthusiasm with which POC tests are being developed, it is likely that they will be used more and more widely. If so, the advantages and limitations of their use should be fully discussed and the implications recognised.

Methods in virus diagnosis: immunofluorescence revisited.

BACKGROUND: Immunofluorescence (IF) has been used in many laboratories for virus diagnosis but has begun to fall inappropriately out of favour as a diagnostic method as pressure on budgets and for objective quality control increases. OBJECTIVES: To review the status, value and benefits of IF. CONCLUSIONS: IF has, we believe, still a valuable role to play in routine virus diagnosis because it is rapid, accurate (with properly validated reagents), flexible and, by giving feedback on the quality of the specimens collected, promotes dialogue with the customer clinicians to their benefit and to that of the diagnostic laboratory. These benefits are not easily duplicated by other methods or techniques. While such rapid diagnosis primarily benefits the individual patient, providing results within a clinically relevant time has a secondary effect of increasing use of the service. It is our experience that the availability of rapid IF diagnosis (as opposed to culture or serology) for respiratory viral infections leads to a substantial increase in its use, thereby enhancing the amount and breadth of the resultant epidemiological data.

The future of diagnostic virology, part 2: staffing the service.

The first part of this review discussed the facilities that are needed to provide a competent diagnostic virology service at the turn of the century. Just as important is to consider who will run it. Hitherto, there have been specialist virologists in most countries. Their roles have evolved with time, developing and running a variety of diagnostic tests, often to answer local needs and their own curiosity, and frequently linked to their research projects. Recently, the advent of an increasingly long list of commercial tests has raised the real possibility of introducing standardized centrally validated testing methods, and using them to bring laboratories up to a similarly uniform level. Unfortunately, they have also had the effect of seeming to make specialist virologists unnecessary, except in a few central reference laboratories. As a consequence, and because of increasing pressure on health service resources, vacated senior virology posts have remained unfilled and this now threatens the career structure of those who want to become, and continue as, virologists. This review explores these issues and offers a possible solution.

Correlation between the detection of viral DNA by the polymerase chain reaction in peripheral blood leukocytes and serological responses to human herpesvirus 6, human herpesvirus 7, and cytomegalovirus in renal allograft recipients.

Diagnosis of significant infections by human herpesvirus 6 (HHV6) and 7 (HHV7) in transplant patients has proved difficult because both viruses are ubiquitous and can cause persistent infections in their hosts. The significance of viral DNA detected in peripheral blood leukocytes (PBLs; DNAemia) by PCR is therefore unclear. The interpretation of serological results is complicated by the fact that both primary and secondary infections with other herpesviruses may be associated with a concurrent antibody response to HHV6. Fifty-four renal allograft recipients were studied prospectively and their serological response to HHV6, HHV7 and CMV were compared with the detection of viral DNAemia from the homologous and heterologous viruses. Serum and heparinished blood samples were collected prospectively from 54 renal allograft recipients. DNA was extracted from PBLs and tested for the presence of HHV6, HHV7 and CMV DNA by PCR. Antibodies to HHV6 and HHV7 were measured by an indirect immunofluorescence test and to CMV by an anticomplement immunofluorescence (ACIF) test. CMV IgM antibodies were detected by a commercial enzyme immunoassay. CMV and HHV7 DNAemia were each significantly associated with serological responses to the homologous virus but no such association was found for HHV6 DNAemia. However, patients with consecutively positive DNAemia to any of the viruses (including HHV6) were more likely to have a homologous serological response. Patients who had detectable CMV IgM without a concurrent rise in CMV antibodies were significantly less likely to have CMV DNAemia (odds ratio = 0.16; 95% CI 0.02-0.9). CMV IgM antibodies may be associated with HHV6 or HHV7 DNAemia (odds ratio 2.3; 95% CI 0.5-15). This serological profile may reflect a crossreactive response to HHV6, HHV7 or other herpesviruses. CMV IgM should not be used in isolation for the diagnosis of CMV infection or disease in this group of patients.

"Cytomegalovirus disease" in renal allograft recipients: is human herpesvirus 7 a co-factor for disease progression?

Fifty-six renal allograft recipients were studied prospectively for 3 months or longer after transplant. The polymerase chain reaction (PCR) was used to screen peripheral blood leucocyte (PBL) specimens for CMV, human herpesvirus 6 (HHV6) and human herpesvirus 7 (HHV7) DNA (DNAemia) in 67 healthy controls and in serial (fortnightly) PBL specimens from the 56 allograft recipients. None of the healthy controls had detectable CMV DNAemia, although HHV6 and HHV7 DNAemia was found in 7% and 9% of individuals respectively. In contrast, DNAemia due to CMV, HHV6 and HHV7 was found in 50%, 36% and 39% of patients respectively, at some time during the post-transplant period. Of the 28 patients who had CMV DNAemia, eight developed "CMV disease". The risk of progression to "CMV disease" was increased in patients with concurrent DNAemia to all three viruses (relative risk 3.7; 95% CI 1.3-10.5). The relative risk of "CMV disease" for patients with concurrent CMV and HHV7 was also increased (RR = 3.5; 95% CI = 1.1-11.6), while the association between CMV and HHV6 was inconclusive (RR = v2.1; 95% CI = 0.7-6.6). The first 26 patients recruited to the study also had serial serum samples tested for antibody responses to the three viruses. "CMV disease" was associated with rising antibody titres to HHV7 (Fisher's exact test, P = 0.02), and weakly so with HHV6 (P = 0.07). It is concluded that in patients with CMV DNAemia, concurrent infection/reactivation HHV7 (and possibly HHV6) is associated with an increased risk of progression to "CMV disease".

Viral infections in children's wards--how well do we manage them?

Children are frequently admitted to hospital wards with viral infections. Many are not life-threatening to the index case, but the spread to vulnerable patients who are already at higher risk should be avoided. To do so requires active awareness and availability of rapid diagnosis (i.e. the same day). Cohorting and handwashing have been found to be the best measures to prevent spread of respiratory syncytial virus (responsible for considerable morbidity every winter) in hospital wards.

Diagnosis of cytomegalovirus (CMV) disease in renal allograft recipients: the role of semiquantitative polymerase chain reaction (PCR).

BACKGROUND: Cytomegalovirus disease remains a significant cause of morbidity and mortality in the renal allograft recipient. There is a need for rapid and sensitive techniques predictive of CMV disease to allow initiation of early antiviral therapy. METHODS: Seventy-seven renal allograft recipients were enrolled in a prospective study where CMV viruria (shell vial culture/DEAFF test), viraemia (shell vial culture), serology and detection of virus DNA in peripheral blood leukocytes by PCR (CMV DNAemia) were correlated with clinical evidence of CMV disease. RESULTS: Serology and shell vial culture had poor sensitivity for the early diagnosis of CMV disease. CMV DNAemia appeared to correlate with active virus replication. CMV DNAemia had a sensitivity and negative predictive value of 100% and a positive predictive value of 27% for CMV disease. Patients with symptomatic CMV disease were shown to have higher levels of CMV DNAemia than those with asymptomatic infection. CONCLUSIONS: A negative CMV DNAemia result excluded CMV disease with confidence, but a positive result (given the low positive predictive value) did not by itself provide a reliable guide for the initiation of pre-emptive antiviral therapy. However, the semiquantitative CMV DNAemia result taken together with the clinical findings provided useful information for patient management.

The complete sequence of a human astrovirus.

We have determined the complete genomic sequence of human astrovirus serotype 1 isolated in Newcastle upon Tyne. The genome is 6813 nucleotides long and contains three sequential open reading frames (ORFs). The two closest to the 5' end are linked by a ribosomal frameshifting motif and contain sequence motifs indicative of non-structural virus proteins: serine protease and RNA-dependent RNA polymerase. A nuclear addressing sequence is also located here. The 3' ORF encodes the virion structural polypeptides as a polyprotein precursor. This genomic organization resembles that of the plant virus family Luteoviridae.