MALDI-TOF analysis of blood serum proteome can predict the presence of monoclonal gammopathy of undetermined significance

Monoclonal gammopathy of undetermined significance (MGUS) is a plasma cell dyscrasia that can progress to malignant multiple myeloma (MM). Specific molecular biomarkers to classify the MGUS status and discriminate the initial asymptomatic phase of MM have not been identified. We examined the serum peptidome profile of MGUS patients and healthy volunteers using MALDI-TOF mass spectrometry and developed a predictive model for classifying serum samples. The predictive model was built using a support vector machine (SVM) supervised learning method tuned by applying a 20-fold cross-validation scheme. Predicting class labels in a blinded test set containing randomly selected MGUS and healthy control serum samples validated the model. The generalization performance of the predictive model was evaluated by a double cross-validation method that showed 88% average model accuracy, 89% average sensitivity and 86% average specificity. Our model, which classifies unknown serum samples as belonging to either MGUS patients or healthy individuals, can be applied to clinical diagnosis.

Using the Electronic Nose to Identify Airway Infection during COPD Exacerbations

BACKGROUND

The electronic nose (e-nose) detects volatile organic compounds (VOCs) in exhaled air. We hypothesized that the exhaled VOCs print is different in stable vs. exacerbated patients with chronic obstructive pulmonary disease (COPD), particularly if the latter is associated with airway bacterial infection, and that the e-nose can distinguish them.

METHODS

Smell-prints of the bacteria most commonly involved in exacerbations of COPD (ECOPD) were identified in vitro. Subsequently, we tested our hypothesis in 93 patients with ECOPD, 19 of them with pneumonia, 50 with stable COPD and 30 healthy controls in a cross-sectional case-controlled study. Secondly, ECOPD patients were re-studied after 2 months if clinically stable. Exhaled air was collected within a Tedlar bag and processed by a Cynarose 320 e-nose. Breath-prints were analyzed by Linear Discriminant Analysis (LDA) with "One Out" technique and Sensor logic Relations (SLR). Sputum samples were collected for culture.

RESULTS

ECOPD with evidence of infection were significantly distinguishable from non-infected ECOPD (p = 0.018), with better accuracy when ECOPD was associated to pneumonia. The same patients with ECOPD were significantly distinguishable from stable COPD during follow-up (p = 0.018), unless the patient was colonized. Additionally, breath-prints from COPD patients were significantly distinguished from healthy controls. Various bacteria species were identified in culture but the e-nose was unable to identify accurately the bacteria smell-print in infected patients.

CONCLUSION

E-nose can identify ECOPD, especially if associated with airway bacterial infection or pneumonia.

Measurement of IgG antibodies to Chlamydia trachomatis by commercial enzyme immunoassays and immunofluorescence in sera from pregnant women and patients with infertility, pelvic inflammatory disease, ectopic pregnancy, and laboratory diagnosed Chlamydia psittaci/Chlamydia pneumoniae infection

BACKGROUND

Screening for Chlamydia trachomatis specific antibodies is valuable in diagnosing asymptomatic pelvic inflammatory disease (PID) and tubal damage following repeated episodes of PID. The assays in current use are unsuitable for screening large numbers of samples so there is a need to develop more suitable assays.

AIMS

To compare the performance of several commercial C trachomatis enzyme immunoassays (EIAs) (SeroCT, C tracho(pep), Medac p-EIA, Vircell and Labsystems C trachomatis IgG EIAs) using major outer membrane protein (MOMP), an inactivated organism EIA (Genzyme Virotech EIA), and a genus specific EIA (Platelia Chlamydia IgG) with the whole cell inclusion immunofluorescence (WIF) assay. In addition, to adapt, using time resolved fluorescence technology, the assay showing the highest correlation with WIF.

METHODS

Ninety sera from patients presenting with ectopic pregnancies, 187 sera from those with a variety of types of infertility, 33 sera from cases of PID where a fourfold rise in WIF titre occurred, and 90 sera from antenatal clinic attenders were tested. A panel of 36 sera from laboratory diagnosed cases of Chlamydia psittaci/Chlamydia pneumoniae infection was also tested.

RESULTS

The Genzyme Virotech EIA showed the highest rank correlation coefficient (0.82) with WIF, particularly at high WIF titres. The MOMP specific assays varied in their correlation with WIF, with rank correlation coefficients ranging from 0.70 (Medac p-EIA) to 0.80 (Vircell EIA). The Genzyme Virotech assay showed poor specificity (5.6%; 95% confidence interval (CI), 0.68% to 18.7%)--it was reactive with 34 of the panel of 36 C psittaci/C pneumoniae positive sera. The MOMP based EIAs showed high specificity, particularly the Medac p-ELISA (97.2%; 95% CI, 85.5% to 99.9%)--only one serum was reactive. In view of the good correlation between WIF and the Genzyme Virotech EIA, a time resolved fluorescence immunoassay (TRFIA) was developed using the Genzyme Virotech antigen. Using an appropriate cut off the TRFIA assay showed excellent correlation with WIF.

CONCLUSIONS

The TRFIA assay may be useful as a screening assay, possibly in conjunction with one of the highly specific EIAs studied (for example, Medac p-EIA) to confirm the antibody specificity of sera selected by the screening assay.

Lidocaine-induced conduction disturbance in patients with systemic hyperkalemia

We report 2 cases in which lidocaine, given for wide-complex tachycardia in the presence of hyperkalemia, precipitated profound conduction disturbance and asystole. The electrophysiologic effects of hyperkalemia and its interaction with lidocaine are reviewed. In patients with known hyperkalemia and wide-complex tachycardia, treatment should be directed at hyperkalemia, rather than following treatment algorithms for wide-complex tachycardia.

How well do viruses survive during transport?

Centralisation of viral diagnostic services offers the potential for cost saving in laboratories, but incurs costs for transporting specimens. In a trial of 326 paired specimens, isolation rates of viruses sent by overnight post and a more expensive same-day courier service were similar.

The laboratory diagnosis of male Chlamydia trachomatis infections--a time for change?

We carried out a two-phased study comparing the effectiveness of first-catch early morning urine (FCU) samples against urethral swabs for the detection of C. trachomatis in men. Four hundred and seventeen new and re-booked consecutive men, who attended the Department of Genito-Urinary Medicine, Bristol, having held their urine overnight, were recruited. Patients who had received antimicrobial chemotherapy in the preceding 2 months were excluded. Early morning FCU samples were obtained from 208 men followed by urethral swabs for the detection of C. trachomatis (phase I) and this order of collection was reversed for the remaining 209 patients (phase 2). A last-catch urine (LCU) was also obtained from all patients. All urethral and urine samples were examined by an amplified enzyme immunoassay (IDEIA, Dako Diagnostics Ltd). Initially, discordant samples were critically examined by direct immunofluorescence (Syva, 'Microtrak') which was used as the 'gold' standard in this study. We have shown that overall 42 and 4.7% of our symptomatic and asymptomatic male patients respectively were positive for C. trachomatis antigen by IDEIA. Furthermore 86.4 and 91.0% (phases 1 and 2) of the total C. trachomatis positive samples were detected by examination of an FCU sample. In contrast only 66.0 and 65.5% (phases 1 and 2) of the total positives were identified by examination of an urethral swab. These results show that an FCU sample not only has the advantage of being a non-invasive procedure but is also a very sensitive method, compared to swabbing the urethra for the detection of C. trachomatis.(ABSTRACT TRUNCATED AT 250 WORDS)

The differentiation of Chlamydia species by antigen detection in sputum specimens from patients with community-acquired acute respiratory infections

An amplified enzyme immunoassay (IDEIA III: Dako Diagnostics Ltd) for detecting genus-specific chlamydia antigen was evaluated prospectively on 286 respiratory specimens from 275 patients presenting with community-acquired pneumonia or persistent chest infection. Nineteen patients had evidence of recent chlamydial infection, having two or more positive sputum or serological markers. Sputa from two other patients were ELISA-positive in the absence of other positive criteria and were regarded as false-positive results. When compared with a direct immunofluorescence test for chlamydial elementary bodies (EBs) using a genus-specific monoclonal antibody, the ELISA gave a positive predictive value of 91% and a negative predictive value of 99%. Non-specific problems with a wide variety of other micro-organisms isolated from the sputa were not encountered. Attempts to differentiate between Chlamydia psittaci, Chlamydia pneumoniae and Chlamydia trachomatis using genus-specific lipopolysaccharide reactive--and species-specific major outer membrane protein--monoclonal antibodies were encouraging and results were substantiated, in most patients, by the species-specific serological assays of the whole-cell-inclusion immunofluorescence or micro-immunofluorescence assays. The study demonstrated that antigen detection techniques offer scope for routine laboratories to diagnose chlamydial respiratory infections rapidly and reliably and may enable differentiation to species level. Although immunofluorescence offers marginally greater sensitivity and specificity when compared with ELISA, the latter is less subjective and less demanding. Sixty-eight per cent of these infections would have remained undiagnosed despite the general availability of ELISA tests.

Chlamydia trachomatis, tubal disease and the incidence of symptomatic and asymptomatic infection following hysterosalpingography

The risk of causing or reactivating pelvic infection by hysterosalpingography (HSG) was assessed in 118 infertile women. Serological evidence of Chlamydia trachomatis infection was sought before, and 10 days and 4 weeks after HSG, using the single-antigen whole-inclusion immunofluorescence (WIF) test for species-specific antibody and the complement fixation test (CFT) for group antibody. Chlamydia antigen was detected using an ELISA. There was a close correlation between the finding of occlusive tubal damage and serum antibodies to C.trachomatis detected by both tests (P less than 0.001). Of 60 patients with WIF antibody titres greater than or equal to 1/64, 65% had evident tubal damage compared with only 16% of patients without a raised titre. Clinically suspected sepsis after HSG occurred in 4% of cases both with and without antibodies to C.trachomatis but only in those with tubal damage (10%). There was no serological evidence of C.trachomatis involvement in symptomatic or asymptomatic patients and anaerobic pathogens were isolated more commonly than C.trachomatis in those symptomatic cases. Isolation of C.trachomatis in two cases from the endocervix and also from the endometrium in one of these only after HSG was compatible with reactivation but not reinfection. Mycobacterium tuberculosis was isolated in two out of three cases with unsuspected tubal disease without antibodies to C.trachomatis. The risk of infection from HSG appears to be confined to patients with existing tubal damage, and in those unexpected cases without serological evidence of previous chlamydial infection, tuberculosis seems to be a likely cause.

Evaluation of three Chlamydia trachomatis immunoassays with an unbiased, noninvasive clinical sample

First-catch early morning urine samples from patients attending a genitourinary medicine clinic were tested by three different enzyme immunoassays. The results suggest significant differences in the sensitivities and specificities of the different assays. The direct visualization of elementary bodies in urine deposits by direct immunofluorescence was used as the "gold standard," using a monoclonal antibody with a different epitope specificity from those of antibodies used in the enzyme-linked immunosorbent assays. We report for the first time that urine specimens represent an unbiased sample, free of the inherent sampling errors associated with other genital specimens. We feel that urine is a valid specimen for use in any evaluation study of new assays directed towards the detection of Chlamydia trachomatis.

The development and evaluation of a mu-capture ELISA detecting Chlamydia-specific IgM

A mu-capture enzyme-linked immunosorbent assay (ELISA) for detecting chlamydia-specific IgM was developed by use of the heat stable, lipopolysaccharide group-specific antigen and an alkaline phosphatase-labelled anti-chlamydia group-specific monoclonal antibody conjugate. The test was used to study the serological response in chlamydial respiratory tract infection among patients with acute respiratory tract symptoms in Cambridgeshire during the past 7 years. Results were compared with those of the complement fixation test (CFT) in routine use as well as those of a whole inclusion indirect immunofluorescence (WIF) test for IgM. Correlation between results of the mu-capture ELISA and those of the WIF test was 87.5%. The percentage of patients in whom specific IgM was found fell with increasing age. This may be due to lack of recall of IgM as a response to reinfection. Chlamydia-specific IgM was more likely to be detected when the CFT titre was greater than or equal to 64 and was rarely detected more than 6 months after the onset of symptoms. However, several patients less than 20 years of age were found to have specific IgM with CF antibody titres less than 64. We have found the mu-capture ELISA a useful test for the diagnosis of respiratory tract chlamydial infections, particularly in younger patients.

Rapid diagnosis of Chlamydia trachomatis infection in patients attending an ophthalmic casualty department

Direct immunofluorescence (DIF) techniques were compared with conventional cell culture for the diagnosis of ocular infections with Chlamydia trachomatis. The DIF test was found to have a sensitivity of 100% and a specificity of 97.5%. Of 178 patients studied, 19 patients (11%) were positive by DIF and 15 (8.4%) by conventional cell culture technique. Four patients who had previous treatment with chloramphenicol eye drops were negative by cell culture but positive by the DIF test. The DIF test is considered to be a rapid, accurate test with a number of advantages over culture techniques for the detection of C. trachomatis. The importance of appropriate referral of positive patients to prevent more serious sequelae due to C. trachomatis infection is discussed.

Enzyme amplified immunoassay: a novel technique applied to direct detection of Chlamydia trachomatis in clinical specimens

Endocervical swabs from 212 women and urethral swabs from 100 men were tested by the routine methods for McCoy cell culture and simultaneously by a novel enzyme amplified immunoassay test to detect chlamydia antigen. Overall correlation of the amplified test with culture was 96.5%. The test proved to be a suitable screening procedure for genital chlamydial infection, particularly for large numbers of specimens or in cases in which culture was not available.

Evaluation of a genus reactive monoclonal antibody in rapid identification of Chlamydia trachomatis by direct immunofluorescence

This study compared the direct visualisation of elementary bodies in urogenital smears by the direct immunofluorescence test with the isolation of Chlamydia trachomatis in McCoy cell cultures treated with cytochalasin B. C trachomatis was isolated from 41 (16.4%) of 250 unselected specimens in McCoy cell cultures treated with cytochalasin B. Of the 41 culture positive specimens 37 (90%) were diagnosed by direct visualisation of elementary bodies in the smears using the direct immunofluorescence test. Four specimens were positive by isolation only and a further seven were positive by the direct immunofluorescence test only. Overall the direct immunofluorescence test had a sensitivity of 90% and a specificity of 97%. The presence of red blood cells or mucus or the use of barrier creams did not appear to interfere with the normal visualisation of elementary bodies using the direct immunofluorescence test.

Isolation of Chlamydia psittaci from cases of conjunctivitis in a colony of cats

This report describes the isolation in cell cultures of Chlamydia psittaci from cases of conjunctivitis in a colony of cats. The organism was identified in McCoy cell monolayers by staining the intracytoplasmic chlamydial inclusions with a fluorescent antibody technique, and serological evidence of chlamydial infection in cats was obtained by indirect immunofluorescence. The possible role of C psittaci as an ocular, upper respiratory and reproductive tract pathogen in cats is discussed.

Value and feasibility of screening women attending STD clinics for cervical chlamydial infections

A chlamydial screening service was provided in Bristol over a three-month period for women attending the sexually transmitted disease (STD) clinic either for the first time or with a new complaint. Isolation of Chlamydia trachomatis was attempted in cytochalasin-treated McCoy cells. Of 919 specimens, valid results were obtained in 796. Chlamydial infections were identified and treated in 154 (19%) of these 796 women. Chlamydia were isolated from 52 (37%) of 152 female partners of men with nongonococcal urethritis (NGU); these patients already routinely receive treatment with tetracylcines in this clinic. The remaining 102 infections (34 (48%) of 71 women with gonorrhoea and 68 (12%) of the other 573 women) would have been unrecognised and usually untreated without chlamydial isolation studies. These figures confirm the need to provide chlamydial diagnostic services for selected STD clinic attenders.