Aud Krook

Detection of Specific IgM Antibodies for the Diagnosis of Mycoplasma pneumoniae Infections: A Clinical Evaluation

The diagnostic value of detection of specific IgM antibodies was analysed in Mycoplasma pneumoniae infections. In a retrospective clinical and serological study, M. pneumoniae IgM antibodies were determined by a mu-capture ELISA using enzyme-labelled antigen. The study group consisted of 91 patients with significantly raised titers in paired sera or a single high titer of complement fixation antibodies. About 40% of the patients had been treated with antibiotics ineffective against M. pneumoniae infections prior to admission to hospital. Treatment with erythromycin or tetracycline was shown to give a shorter period of fever compared to if no or ineffective therapy was given. Specific IgM antibodies were detected in about 80% of sera sampled 9 days or more after onset of symptoms. In sera sampled at 7-8 days after onset IgM antibodies were found in about 40% of the sera but only occasionally in sera sampled earlier. In the age group 0-20 years 88% of the patients developed an IgM response. In the higher ages (greater than 60 years) a significantly lower rate of IgM responders was observed.

Screening for human T cell leukaemia/lymphoma virus among blood donors in Sweden: cost effectiveness analysis

Abstract Objective: To analyse the cost effectiveness of a national programme to screen blood donors for infection with the human T cell leukaemia/lymphoma virus. Design: Three models for calculating the costs and benefits of screening were developed. The first model analysed the cost of continuously testing all donations; the second analysed the cost of initially testing new blood donors and then retesting them after five years; the third analysed the cost of testing donors only at the time of their first donation. Patients who had received blood components from donors confirmed to be infected with the virus were offered testing. Setting: Sweden. Main outcome measures: Prevalence of infection with the virus among blood donors, the risk of transmission of the virus, screening costs, and the outcome of infection. Results: 648 497 donations were tested for the virus; 1625 samples tested positive by enzyme linked immunosorbent assay. 6 were confirmed positive by western blotting. The prevalence of infection with the virus was 2/100 000 donors. 35 patients who had received blood infected with the virus were tested; 3 were positive. The cost of testing every donation was calculated to be

Lack of serotype-specific antibody response to lipopolysaccharide antigens ofMoraxella catarrhalis during lower respiratory tract infection

3.02m (£1.88m); this is 18 times higher than the cost of testing new donors only, and only 1 additional positive donor would be discovered in 7 years. Regardless of the model used, screening was estimated to prevent only 1 death every 200 years at a minimum cost of

Rapid aetiological diagnosis of pneumonia based on routine laboratory features.

36m (£22.5m). Conclusion: Based on these estimates the Swedish National Board of Health and Welfare decided that only new blood donors would be screened for infection with the virus. Key messages The human T cell leukaemia/lymphoma virus is primarily sexually transmitted; it may also be transmitted through blood transfusions Infection with the virus may cause adult T cell leukaemia/lymphoma or tropical spastic paraparesis Many countries including Sweden have begun screening blood donors for the virus; however a low prevalence of infection in non-endemic areas a low risk of developing adult T cell leukaemia/lymphoma in people infected with the virus a long incubation period and the older age of most transfusion recipients make screening costly Three models of screening were compared: testing every donation, testing new donors and then retesting them after five years, and testing new donors only Regardless of the model used screening in Sweden would only prevent one death every 200 years at a minimum cost of

Etiologic diagnosis of pneumonia by antigen detection: Crossreactions between pneumococcal C-polysaccharide and oral microorganisms

36m (£22.5m)

Prevalence and risk factors for HTLV-II infection in 913 injecting drug users in Stockholm, 1994

An enzyme immunoassay (EIA) was used to determine the antibody response to different serotypes of lipopolysaccharide (LPS) antigens ofMoraxella catarrhalis in adult patients with lower respiratory tract infections (LRTI).Moraxella catarrhalis was isolated from sputum or nasopharyngeal samples from 20 patients with LRTI. Sixteen of the isolates were serotype A, four were type B and none were type C. The antibody response to the different LPS serotypes was determined in paired sera from patients suffering from LRTI. In addition to the 20 patients withMoraxella catarrhalis isolated (Group 1), a group of seven patients with LRTI of unknown etiology (Group 2) and a group of ten patients with LRTI of known other bacterial etiology (Group 3) were selected for this study. An increase in antibody levels of > 1.5-fold (convalescent/acute-phase serum) was recorded in approximately half of the patients, not only in the first group (Moraxella catarrhalis isolated) but also in the other two groups. However, in the first and second groups there was a correlation between an increase in antibody levels in the LPS EIA and in an EIA using whole bacterial cells as antigen. In the group of patients in whomMoraxella catarrhalis was isolated, the antibody response to LPS antigens was not serotype specific. The antibody response to type-A and type-B LPS was more predominant than the response to type-C LPS in most patients. The results show that an antibody response to LPS antigens during lower respiratory tract infections caused byMoraxella catarrhalis could be demonstrated and that there was a correlation between the response found in a whole-cell EIA and the LPS EIA. However, titre increases, especially to type-A LPS, were recorded in seven of ten patients with LRTI of other bacterial etiology. Serological investigations based on determination of antibodies to LPS antigens were not useful for etiological studies but may be of interest for studying the pathogenetic mechanisms of respiratory tract infections.

Comparison of three methods for detection of pneumococcal antigen in sputum of patients with community-acquired pneumonia

The values of some basic laboratory features on admission to hospital were recorded and compared in 418 adult patients with community-acquired pneumonia, namely erythrocyte sedimentation rate, C-reactive protein, white blood cell (WBC) count, serum lactate dehydrogenase (S-LD), serum alanine-aminotransferase, and serum sodium. Discriminant analysis was performed to obtain an aetiological diagnosis. WBC value of greater than 15 x 10(9)/l strongly indicated a bacterial and, especially a pneumococcal aetiology, whereas increased S-LD could imply a mycoplasmal infection. For patients less than 50 years of age the equation C2 = -1.788 + 0.204 x WBC-0.0909 X S-LD was constructed, in which C2 greater than 0 indicated a pneumococcal aetiology. This function correctly classified 31/33 (93.9%) patients with a mycoplasmal and 20/31 (64.5%) patients with a pneumococcal infection. Patients with viral, Haemophilus influenzae or chlamydial infection could not be discriminated from each other. The age of the patient, WBC and possibly S-LD on admission are easily accessible parameters and these results could therefore be of value in daily clinical practice in hospitals.

Antibiotic Therapy in Pneumonia: A Comparative Study of Parenteral and Oral Administration of Penicillin

Crossreactions between bacteria occurring more or less frequently in the respiratory tract were investigated using an enzyme-linked immunosorbent assay (ELISA) developed for the detection of pneumococcal C-polysaccharide. A collection of 218 strains was investigated: 30 Streptococcus pneumoniae, 120 alpha-streptococci, and 68 strains representing other species. Strong crossreactions were observed with 36% of the alpha-streptococci and with two of 11 Staphylococcus aureus strains. The collection of alpha-streptococci consisted of 90 fresh clinical isolates and 30 stock strains. Almost all crossreactions of alpha-streptococci were found among the clinical isolates. Among the stock strains only one of four Streptococcus mitis strains was positive. Pneumococcal C-polysaccharide and phosphorylcholine inhibited the reactions in ELISA with monoclonal antibodies against pneumococcal C-polysaccharide, as well as with a polyclonal antiserum against pneumococcal C-polysaccharide. We suggest that the cross reactions between alpha-streptococci and pneumococci depend on the presence of phosphorylcholine as a common antigenic determinant. The crossreaction in the ELISA with some Staphylococcus aureus strains may be explained by the presence of protein A binding to the Fc portion of the antibodies. When the 10 alpha-streptococci that showed the strongest crossreactions and ten pneumococci representing different types were tested in different concentrations the absorbance values were lower for most alpha-streptococci compared with the pneumococci. This explains that false positive results with alpha-streptococci do not seem to constitute a practical problem in this ELISA developed for detection of pneumococcal C-polysaccharide in samples from patients with pneumonia.

Enzyme-linked immunosorbent assay for detection ofMycoplasma pneumoniae specific immunoglobulin M

The prevalence and risk factors for acquisition of human T-cell lymphotropic virus type I and II (HTLV-I and II) were investigated in a prospective study of 913 injecting drug users (IDUs) in Stockholm in 1994. Epidemiologic data were recorded, and blood samples were tested for antibodies against HTLV-I and HTLV-II; human immunodeficiency virus (HIV) types 1 and 2; and hepatitis A (HAV), B (HBV), C (HCV), and D (HDV). Positive serologic results for HTLV were confirmed by Western blot (WB) and polymerase chain reaction (PCR). Of the 905 participants with conclusive HTLV-II status, 29 (3.2%) were HTLV-II positive, and all but three were of Nordic descent. None was HTLV-I infected. One person was infected as early as 1981, before HIV had reached the IDU population in Sweden. The prevalence of HTLV-II infection was 12% among HIV-1-seropositive and 1.8% among HIV-1-seronegative participants. The overall seroprevalences were 14% for HIV-1, 0% for HIV-2, 41% for HAV, 75% for HBV, 92% for HCV, and 8% for HDV. Although amphetamine has been the main injecting drug in Sweden for several decades, heroin abuse combined with a debut of injecting drugs before 1975 was identified as the most important risk factor associated with HTLV-II infection. HAV and HIV seropositivity were also independent risk factors.

HTLV-II Among Injecting Drug Users in Stockholm

In a prospective study of 249 patients with community-acquired pneumonia, three tests for the detection of pneumococcal antigen in sputum were compared: a coagglutination test for detecting capsular antigens (Cap-CoA), a sandwich enzyme immunoassay (PnC-EIA) and a coagglutination test (PnC-CoA), both the latter detecting the pneumococcal C-polysaccharide common to all pneumococcal types. Sixty-three patients had culture-positive pneumococcal pneumonia, 45 pneumonia caused by other bacteria and 141 pneumonia of viral or unknown etiology. The sensitivity of Cap-CoA (63%) and PnC-CoA (65%) was somewhat higher than that of PnC-EIA (49%), but not significantly so. The specificity was 96–98% for all three methods. Using PnC-CoA 66 patients with possible pneumococcal infection were detected, the diagnosis being verified by culture in 41. Using Cap-CoA 59 such patients were detected, the diagnosis being verified in 40, and using the PnC-EIA 47 such patients were detected, the diagnosis being verified in 31. Antigen was found almost as often in non-purulent as in purulent samples, and as often in washed as in non-washed purulent samples. However, antibiotic treatment before the sputum sample was obtained resulted in significantly lower sensitivity of both PnC-CoA and Cap-CoA. This study confirms the high sensitivity and specificity of methods for pneumococcal antigen detection in sputum. Since CoA is easier and quicker to perform, and cheaper than the EIA, either PnC-CoA or Cap-CoA would seem to be the technique of choice for detection of pneumococcal antigen, whereby all sputum samples, including non-purulent samples, can be used.