Estimating anchor-based minimal important change using longitudinal confirmatory factor analysis

PURPOSE

The minimal important change (MIC) is defined as the smallest within-individual change in a patient-reported outcome measure (PROM) that patients on average perceive as important. We describe a method to estimate this value based on longitudinal confirmatory factor analysis (LCFA). The method is evaluated and compared with a recently published method based on longitudinal item response theory (LIRT) in simulated and real data. We also examined the effect of sample size on bias and precision of the estimate.

METHODS

We simulated 108 samples with various characteristics in which the true MIC was simulated as the mean of individual MICs, and estimated MICs based on LCFA and LIRT. Additionally, both MICs were estimated in existing PROMIS Pain Behavior data from 909 patients. In another set of 3888 simulated samples with sample sizes of 125, 250, 500, and 1000, we estimated LCFA-based MICs.

RESULTS

The MIC was equally well recovered with the LCFA-method as using the LIRT-method, but the LCFA analyses were more than 50 times faster. In the Pain Behavior data (with higher scores indicating more pain behavior), an LCFA-based MIC for improvement was estimated to be 2.85 points (on a simple sum scale ranging 14-42), whereas the LIRT-based MIC was estimated to be 2.60. The sample size simulations showed that smaller sample sizes decreased the precision of the LCFA-based MIC and increased the risk of model non-convergence.

CONCLUSION

The MIC can accurately be estimated using LCFA, but sample sizes need to be preferably greater than 125.

Responsiveness and Minimal Important Change of the PROMIS Pain Interference Item Bank in Patients Presented in Musculoskeletal Practice

We evaluated the responsiveness of the Patient Reported Outcome Information System Pain Interference item bank in patients with musculoskeletal pain by testing predefined hypotheses about the relationship between the change scores on the item bank, change scores on legacy instruments and Global Ratings of Change (GRoC), and we estimated Minimal Important Change (MIC). Patients answered the full Dutch-Flemish V1.1 item bank. From the responses we derived scores for the standard 8-item short form (SF8a) and a CAT-score was simulated. Correlations between the change scores on the item bank, GRoC and legacy instruments were calculated, together with Effect Sizes, Standardized Response Means, and Area Under the Curve. GRoC were used as an anchor for estimating the MIC with (adjusted) predictive modeling. Of 1,677 patients answering baseline questionnaires 960 completed follow-up questionnaires at 3 months. The item bank correlated moderately high with the GRoC (Spearman's rho 0.63) and with the legacy instruments (Pearson's R ranging from .45 to .68). It showed a high ES (.97) and Standardized Response Means (.71), and could distinguish well between improved and not improved patients based on the GRoC (Area Under the Curve .77). Comparable results were found for the derived SF8a and CAT-scores. The MIC was estimated to be 3.2 (CI 2.6-3.7) T-score points. PERSPECTIVE: Our study supports the responsiveness of the PROMIS-PI item bank in patients with musculoskeletal complaints. Almost all predefined hypotheses were met (94%). The PROMIS-PI item bank correlated well with several legacy instruments which supports generic use of the item bank. MIC for PROMIS-PI was estimated to be 3.2 T-score points.

Pain trajectories and possible predictors of a favourable course of low back pain in patients consulting musculoskeletal physicians in The Netherlands

BACKGROUND

In The Netherlands, low back pain patients can consult physicians specialized in musculoskeletal (MSK) medicine. Previous studies have reported on the characteristics of patients consulting MSK physicians, and the treatment options used. There are no studies yet reporting on the course of Low Back Pain (LBP) after treatment by musculoskeletal (MSK) physicians in The Netherlands.

METHODS

In an observational cohort study MSK physicians recorded data about all low back pain patients presenting for a first consultation. At baseline they recorded age, gender, type and duration of the main complaint, and concomitant complaints. At the end of treatment they recorded the type of treatment and the number of treatment sessions. Patients were recruited to answer questionnaires at baseline, and at 6-weekly intervals during a follow-up period of six months. Patient questionnaires included information about previous medical consumption, together with PROMs measuring the level of pain and functional status. Latent Class Growth Analysis (LCGA) was used to classify patients into different groups according to their pain trajectories. Baseline variables were evaluated as predictors of a favourable trajectory using logistic regression analyses, and treatment variables were evaluated as possible confounders.

RESULTS

A total of 1377 patients were recruited, of whom 1117 patients (81%) answered at least one follow-up measurement. LCGA identified three groups of patients with distinct pain trajectories. A first group (N = 226) with high pain levels showed no improvement, a second group (N = 578) with high pain levels showed strong improvement, and a third group (N = 313) with mild pain levels showed moderate improvement. The two groups of patients presenting with high baseline pain scores were compared, and a multivariable model was constructed with possible predictors of a favourable course. Male gender, previous specialist visit, previous pain clinic visit, having work, a shorter duration of the current episode, and a longer time since the complaints first started were predictors of a favourable course. The multivariable model showed a moderate area under the curve (0.68) and a low explained variance (0.09).

CONCLUSIONS

In low back pain patients treated by musculoskeletal physicians in The Netherlands three different pain trajectories were identified. Baseline variables were of limited value in predicting a favourable course.

A confirmatory factor analysis approach was found to accurately estimate the reliability of transition ratings

INTRODUCTION

Transition ratings (TRs) are single item measures which ask patients to report on their health change. They allow for a simple assessment of improvement or deterioration and are frequently used as an "anchor" to determine interpretation thresholds on a patient-reported outcome measure (PROM). Despite their widespread use, a routinely applicable method to assess their reliability is lacking. This paper introduces a method to estimate the reliability of TRs based on confirmatory factor analysis (CFA) for categorical data.

METHOD

We modelled longitudinal PROM data as independent factors representing Time 1 and Time 2 in a CFA model. PROM items taken at Time 1 (T1) loaded on the first factor, although the same items taken at Time 2 (T2) loaded on the second. The TR item loaded onto both T1 and T2 factors. Three models with various constraints on the loadings and thresholds were examined. The communality (R²) statistic was used as a measure of the TR reliability. The approach was evaluated using simulated data and exemplified in four empirical datasets.

RESULTS

The simplest CFA model without constraints on the item loadings and thresholds performed equivalently to models with constraints on loadings and thresholds over time. Further constraints on the TR item loadings to be equal and opposite over time caused biased TR reliability estimates if the T1 and T2 loadings differed in magnitude. In the four empirical datasets, reliability of TRs ranged from 0.27 to 0.48. In three examples the TR had numerically stronger loading on T2 than on T1.

DISCUSSION AND CONCLUSIONS

Results support the use of the proposed method in understanding the reliability of TRs. Empirical study results reflect the typical range of reliability that has previously been reported for single items. Methodological considerations to improve TR reliability are presented, and developments of this method, are posited.

Psychometric properties of the Dutch-Flemish Patient-Reported Outcomes Measurement Information System Pain Behavior item bank in patients with musculoskeletal complaints

We studied the psychometric properties of the 39-item v1.1 Dutch-Flemish Patient-Reported Outcomes Measurement Information System Pain Behavior item bank in a sample of 1,602 patients with musculoskeletal complaints. We evaluated the assumptions of the underlying item response theory (IRT) model (unidimensionality and local dependency with confirmatory factor analyses), and monotonicity with scalability coefficients). We studied the IRT model fit of all items and estimated the item parameters of the IRT model. Differential item functioning (DIF) was studied for age and gender, and DIF for language was studied as a measure of cross-cultural validity. Confirmatory factor analyses showed suboptimal fit of a unidimensional model, but a bifactor model showed low risk of bias when a unidimensional model was assumed (Omega H = .92, explained common variance of .70). Fifteen item pairs (2%) were locally dependent. Five items showed poor scalability. All items fitted the IRT model; slope parameters ranged from .60 to 2.00, and threshold parameters from -2.05 to 6.80. One item showed DIF for age, 1 item DIF for gender, and 5 items showed DIF for language, but the impact on total scores was low. Our study shows limitations of the Dutch-Flemish Patient-Reported Outcomes Measurement Information System Pain Behavior item bank when used in a primary care population with musculoskeletal complaints. PERSPECTIVE: We studied the psychometric properties of the Dutch-Flemish Patient-Reported Outcomes Measurement Information System Pain Behavior item bank in a large primary care population of patients with musculoskeletal complaints. It showed that the Pain Behavior item bank has limitations when used in this population.

Physicians using spinal manipulative treatment in The Netherlands: a description of their characteristics and their patients

Background

Various health care professionals apply Spinal Manipulative Treatment (SMT) in daily practice. While the characteristics of chiropractors and manual therapists and the characteristics of their patient populations are well described, there is little research about physicians who use SMT techniques. A distinct group of physicians in The Netherlands has been trained in musculoskeletal (MSK) medicine, which includes the use of SMT. Our objective was to describe the characteristics of these physicians and their patient population.

Methods

All registered MSK physicians were approached with questionnaires and telephone interviews to collect data about their characteristics. Data about patient characteristics were extracted from a web-based register. In this register physicians recorded basic patient data (age, gender, the type and duration of the main complaint, concomitant complaints and the type of referral) at the first consultation. Patients were invited to fill in web-based questionnaires to provide baseline data about previous treatments and the severity of their main complaint. Functional impairment was measured with Patient Reported Outcome Measures (PROMs).

Results

Questionnaires were sent to 138 physicians of whom 90 responded (65%). Most physicians were trained in MSK medicine after a career in other medical specialities. They reported to combine their SMT treatment with a variety of diagnostic and treatment options part of which were only permissible for physicians, such as prescription medication and injections. The majority of patients presented with complaints of long duration (62.1% > 1 year), most frequently low back pain (48.1%) or neck pain (16.9%), with mean scores of 6.0 and 6.2, respectively, on a 0 to10 numerical rating scale (NRS) for pain intensity. Mean scores on all PROMs showed moderate impairment. Patients most frequently reported previous treatment by physical therapists (68.1%), manual therapists (37.7%) or chiropractors (17.0%).

Conclusion

Our study showed that MSK physicians in The Netherlands used an array of SMT techniques. They embedded their SMT techniques in a broad array of other diagnostic and treatment options, part of which were limited to medical doctors. Most patients consulted MSK physicians with spinal pain of long duration with moderate functional impairment.

The influence of study population and definition of improvement on the smallest detectable change and the minimal important change of the neck disability index

Background

Reported values of the minimal important change (MIC) and the smallest detectable change (SDC) for the neck disability index (NDI) differ strongly, raising questions about the generalizability of these parameters. The SDC and the MIC are possibly influenced by the study design or by the study population. We studied the influence of the type of anchor, the definition of improvement and population characteristics on the SDC and the MIC of the NDI.

Methods

A cohort study including 101 patients with non-specific, chronic neck pain. SDC and MIC were calculated using two types of external anchors. For each anchor we applied two different definitions to dichotomize the population into improved and unimproved patients. The influence of patient characteristics was assessed in relevant subgroups: patients with or without radiating pain and patients with different baseline scores.

Results

The influence of different anchors and different definitions of improvement on estimates of the SDC and the MIC was only minimal. The SDC and the MIC were similar for subgroups of patients with or without radiation, but differed strongly for subgroups of patients with higher or lower baseline scores.

Conclusions

Our study shows that estimates of the SDC and the MIC of the NDI can be influenced by population characteristics. It is concluded that we cannot adopt a single change score to define relevant change by combining the result of previous studies.

Variance in Manual Treatment of Nonspecific Low Back Pain Between Orthomanual Physicians, Manual Therapists, and Chiropractors

OBJECTIVE

The aim of the study was to identify differences in the diagnosis and treatment of nonspecific low back pain among 3 professional groups in the Netherlands: orthomanual physicians, manual therapists, and chiropractors.

METHODS

Information was obtained from training materials from professional groups, literature searches, and observation of selected practitioners at work.

RESULTS

In The Netherlands, there are differences in education between the 3 professional groups. The focus of orthomanual medicine is on abnormal positions of components of the skeleton and symmetry in the spine. Manual therapy focuses on functional disorders of the musculoskeletal system. Chiropractic focuses on the musculoskeletal and nervous systems in relation to patients' health in general. Orthomanual medicine considers inspection and palpation the most important diagnostic tools. Manual therapists and chiropractors additionally perform tests to determine functional disorders and manual therapists evaluate psychosocial influences. Chiropractors take radiographs if necessary. Orthomanual physicians apply mobilization techniques using fixed protocols. Manual therapists and chiropractors use various manipulation and mobilization techniques and their manipulation techniques differ in amplitude and velocity.

CONCLUSIONS

Diagnostic techniques and treatment methods of the 3 professional groups differ considerably. For more accurate reporting of the efficacy of manipulative and mobilizing therapies, the characteristics of treatments should be described in more detail when reported in studies such as randomized clinical trials.

Substances with estrogenic activity in effluents of sewage treatment plants in southwestern Germany. 2. Biological analysis

The proliferation test with human estrogen receptor-positive MCF-7 breast cancer cells (E-Screen assay) was applied for quantitative determination of total estrogenic activity in 24-h composite effluent samples from 16 municipal and two industrial sewage treatment plants (STPs) in the state of Baden-Württemberg, southwestern Germany. The estrogenic efficacy relative to the positive control, 17beta-estradiol, was between 26 and 74% (median, 48%) for the 16 municipal STPs. Estradiol equivalent concentrations (EEQs) were between 0.2 and 7.8 ng/L (median, 1.6 ng/L) and, thereby, were lower than those found in a pilot study, which revealed EEQs of greater than 10 ng/L in the effluents of two other STPs. The EEQs in 14 of the 16 effluent samples were very similar (0.9-3.3 ng/L), indicating a rather constant input of estrogenic substances via STPs into rivers. Additional activated charcoal filtration turned out to be very efficient in further eliminating estrogenic activity from effluents. The EEQs of the E-Screen assay and those calculated from the results of extensive chemical analysis using the estradiol equivalency factors determined for 13 natural and synthetic estrogenic substances were comparable for most of the effluent samples. 17beta-Estradiol, 17alpha-ethinylestradiol, and, to a lesser extent, estrone contributed to 90% or more of the EEQ value.

Input/output balance of estrogenic active compounds in a major municipal sewage plant in Germany

24 h samples of untreated and treated wastewater were taken in parallel from a modern municipal sewage plant in southern Germany in March and June 1998. After solid phase extraction, total estrogenic activity was quantitatively measured with a miniaturized E-screen assay and the levels of nine estrogenic phenolic chemicals analyzed by HRGC/LRMS. 17Beta-estradiol equivalent concentrations (EEQ) were 58 and 70 ng/l in the influent and 6 ng/l in the effluent, indicating that the load of estrogenic activity of the wastewater was reduced by about 90% in the sewage plant. Less than 3% of the estrogenic activity was found in the sludge. 4-t-octylphenol, 4-nonylphenol, bisphenol A, 2-hydroxybiphenyl, and 4-chloro-3-methylphenol were detected in the untreated wastewater at levels from 0.13 to 3.6 microg/l. 4-t-octylphenol, 4-nonylphenol, and bisphenol A were present in the effluent at concentrations from 0.16 to 0.36 microg/l, 2-hydroxybiphenyl and 4-chloro-3-methylphenol were not detectable. The contribution of the quantified levels of phenolic xenoestrogens to total estrogenic activity in the sewage was 0.7-4.3%.

Pitfalls in the application of enzyme-linked immunoassays for the detection of circulating trypanosomal antigens in serum samples

The experimental infection of two goats with Trypanosoma vivax trypanosomes provided samples for analysis using parasitology techniques and antigen-detection enzyme-linked immunosorbent assays (ELISAs) for T. vivax, T. congolense and T. brucei. Clinical, parasitological and serological findings were monitored during the course of infection to identify problems in the application of these ELISAs. The data clearly showed that the ELISAs examined were entirely unsuitable for the reliable detection of trypanosomal antigen. Consequently, research strategies pertinent to the development of a new generation of both antigen and antibody ELISAs are outlined considering the problems encountered. These were (1) the reactivity of the reagents; (2) the specificity of the reagents; (3) the nature of the test sample, e.g. the compartmentalisation of trypanosomes between plasma, serum and red blood cells; (4) possible interference with the ELISA through immune complexing; and (5) the biology of the host/trypanosome relationship to gain an understanding of fluctuations in trypanosomes in the systemic circulation.

Development of a sensitive E-screen assay for quantitative analysis of estrogenic activity in municipal sewage plant effluents

A simplified proliferation test with human estrogen receptor-positive MCF-7 breast cancer cells (E-screen assay) was optimized and validated for the sensitive quantitative determination of total estrogenic activity in effluent samples from municipal sewage plants. After solid phase extraction of 1 l sewage on either 0.2 g polystyrene copolymer (ENV+) or 1 g RP-C18 material and removal of the solvent, analysis of the extracts in the E-screen assay could be performed without any clean-up step. This was even possible with untreated sewage. Parallel extraction of four sewage samples on both different solid phase materials gave comparable quantitative results in the E-screen. A blank sample did not induce cell proliferation. As additive behaviour of the estrogenic response of single compounds was proven for two different mixtures each containing three xenoestrogens, total estrogenic activity in the sewage samples, expressed as 17 beta-estradiol equivalent concentration (EEQ), could be calculated comparing the EC50 values of the samples with those of the positive control 17 beta-estradiol. The detection limit of the E-screen method was 0.05 pmol EEQ/l (0.014 ng EEQ/l), the limit of quantification 0.25-0.5 pmol EEQ/l (0.07-0.14 ng EEQ/l). In total, extracts of nine effluent and one influent sample from five different municipal sewage plants in South Germany were analyzed in the E-screen. All samples strongly induced cell proliferation in a dose-dependent manner which was completely inhibited by coincubation with 5 nM of the estrogen receptor-antagonist ICI 182,780. The proliferative effect relative to the positive control 17 beta-estradiol (RPE) was between 30 and 101%. 17 beta-Estradiol equivalent concentrations were between 2.5 and 25 ng/l indicating a significant input of estrogenic substances via sewage treatment plants into rivers.

Validation and application of a rapid in vitro assay for assessing the estrogenic potency of halogenated phenolic chemicals

The E-Screen assay serves as an in vitro tool for the detection of estrogenic activity of chemicals and extracts of environmental samples. Based on the induction of proliferation in human estrogen receptor-positive MCF-7 breast cancer cells we could substantially simplify the assay. As one important step of validation we applied the modified assay for testing nine known xenoestrogens. We could confirm the results of other groups assuring the reproducibility of the E-Screen assay. The results provide evidence that the E-Screen assay is suitable for determination of estradiol equivalency factors (EEFs) for environmental estrogens to rank their estrogenic potency relative to the natural estrogen 17 beta-estradiol. Further, we used the optimized proliferation test to screen nine halogenated phenolic compounds for their possible estrogenic potency. Three widely applied chemicals expressed a weak receptor-mediated estrogenic activity: the flame retardant Tetrabromo-Bisphenol-A, the disinfectant 4-chloro-3-methylphenol, and the herbicide educt 4-chloro-2-methylphenol. Their estrogenic potencies were five to six orders of magnitude lower than that of 17 beta-estradiol.

[Continuation of the observation and serological investigation of a Maedi-Visna virus infected sheep flock from January 1990 to June 1996]

This paper describes the second part of a longtime-study, started in 1987. Serologic investigations for detecting antibodies against Maedi Visna-virus (MVV) were performed, involving an institute own sheep flock. The method used was the immunodiffusiontest. The flock consisted of different breeds and their offsprings. So far, the virus seems to persist in the herd. This work also shows the importance of the central role of the does for spreading the virus. Seroconversion was detected in a sheep at the age of 32 months. The mother of this sheep was a thoroughbred and MVV-negative mountain sheep. After removal of the animals with high antibody (ab)-titers, until the end of 1991, the percentage of seronegative sheep increased. Then seropositive sheep didn't show high ab-titers anymore. Since 1990 only offsprings increased the size of the herd. The health status of the flock was clinically inconspicuous. It can be concluded that in spite of good food quality, good hygiene, without culling positive animals and just giving away accidentally some sheep, no elimination of MVV was registered in the flock over a period of more than six years. There was only seen a reduction of seropositive animals. Single results of serological tests, without knowing the sheep and the serological status of the herd, could pretend a false negative status.

The adhesion molecule E-cadherin and a surface antigen recognized by the antibody 9C4 are selectively expressed on erythroid cells of defined maturational stages

The antigen expression of immature erythroid bone marrow cells was studied using two recently generated monoclonal antibodies (mAb), mAb 67A4 and 9C4, with specificities for the epithelial cell adhesion molecule E-cadherin (E-cad; mAb 67A4), and a novel 110 kDa differentiation antigen (mAb 9C4) with unknown molecular structure. Pappenheim staining of FACS-purified cells labeled with mAb 9C4 and anti-glycophorin A (GA) revealed that the majority of the 9C4+GA- and 9C4+GA+ cells consisted of erythroblasts. In contrast, the E-cad-positive population comprised normoblasts and erythroblasts. While the E-cad+GA- fraction contained mainly erythroblasts and basophilic normoblasts, the E-Cad+GA+ population was enriched in orthochromatic and polychromatophilic normoblasts. By colony assays of affinity column-purified cells it could be shown that erythroid colony forming units (CFU-E) were enriched and erythroid burst forming units (BFU-E) were depleted in the 9C4- and E-cad-positive fractions. Flow cytometric analysis of bone marrow cells double-labeled with mAb 67A4 and anti-CD71, anti-CD117, anti-CD34, or anti-GA revealed that about 90% of the E-cad-positive cells coexpressed CD71, about 70% were positive for CD117, about 50% for GA, and only about 5% coexpressed CD34. The expression pattern of 9C4 antigen was similar to that of E-Cad with the exception that only a minority of the 9C4-positive cells coexpressed GA. Lymphoid and myeloid markers were negative on both the E-Cad- and 9C4-positive populations. In these studies we describe the identification of a new mAb-defined antigen which is specifically expressed on erythroblasts and CFU-E(9C4) and demonstrate that E-Cad is not only expressed on epithelial cells but also on erythropoietic cells of defined maturational stages.

[Isolation of the agent of European swine plague from imported frozen wild boar meat]

Since July 1993 imported frozen meat of wild boars has to be screened for the presence of HCV. The number of taken samples is given by the Ministry of health, sport and consumer protection. Until August 1994 the total number of 688 samples from different countries, have been examined. Three of them were found positive for HCV. The first one (November 1993) was from China, the other two positive samples were sent in one delivery from Romania in May 1994.

Seroprevalence survey for Anaplasma marginale-infection of Austrian cattle

A serologic survey study of 5,076 Austrian cattle farming herds was carried out in the period of December 1988 till March 1990. One animal was randomly selected from each herd and the antibody titer against Anaplasma marginale in blood serum samples was evaluated by means of the complement fixation test. The number of these tested blood samples was 3.6% of 140,081 cattle herd farms of Austria. 109 (2.1%) of the tested animals showed positive titers (1:10) against Anaplasma marginale, in relation to the 140,081 cattle herds 0.08%, 4,786 (94.3%) blood serum samples were sero-negative, 188 (3.8%) reacted anticomplementary. The highest number of antibody-positive animals of 8 tested Austrian districts could be found in Carinthia (46 = 5.7%). In Burgenland all tested sera turned out to be negative. Concerning the distribution of sero-positive animals in Austria it can be stated that a decrease of positive reactors from southern to northern region is evident. A connection between the occurrence of anaplasmosis in Italy, Yugoslavia, Switzerland and Hungary, is postulated as a result of the different systems of keeping cattle in the provinces and the regional increase of tick invasion. Possibly an intensive animal transportation is of importance due to the introduction of the disease mentioned before. The results obtained show that anaplasmosis does occur in different areas of Austria. For control of this disease in Austria it is proposed that all imported cattle should be tested serologically for antibodies against Anaplasma marginale. Other diseases in connection with anemia should be excluded by clinical, serological, blood-, as well as pathological examinations.

Evidence that the sheep associated form of malignant catarrhal fever is caused by a herpes virus

Out of a cow, which was infected with the sheep form of malignant catarrhal fever (MCF), blood and spleen samples were inoculated into rabbits. From the spleen cells of an infected rabbit, which were cocultivated with bovine embryonic gingiva cells, a herpesvirus could be isolated. The isolate showed crossreactions with reference sera against the strain WC 11 (wildebeest form) in the SNT. An immunosuppressed heifer, which was infected with the isolate, contracted typical clinical symptoms of MCF. The isolate was named No. 732.

[Serological studies of antibodies against maedi-visna virus in sheep in Austria]

883 sheep from 68 flocks were tested for the prevalence of antibodies against Maedi/Visna-(M/V)virus. As serological method the Agar Gel Immunodiffusion Test (AGID) was performed, 9.5% of the blood samples were positive against M/V, 1.7% showed questionable results. The highest incidence of serum-antibodies showed the Texel (47.7%) and Milk sheep (26.1%). No antibody titers were found in Mountain and Suffolk sheep. Merino sheep had antibody titers against M/V in 2.6% and Mountain sheep crossbreeds in 1.7%.

[Serologic progression studies using CF and ELISA for the detection of antibodies against Eperythrozoon suis infection of swine]

Serological studies by means of a CF-Test and Elisa were undertaken for evaluation of antibody titers against Eperythrozoon suis infection in swine. The animals were partly splenectomized and underwent artificial infection. It could be shown that the splenectomized animals showed higher and longer lasting antibody titers than the non splenectomized swine. It is stated, that the above mentioned tests can be used in diagnosis on a herd basis but not on a single animal basis.

[Results of a serological study of the natural spread of maedi-visna virus infection in a sheep herd during an observation period of 30 months]

In a sheep population consisting of animals of different breeds the epidemiologic development of the Maedi-Visna-infection was evaluated by means of monthly Immune Diffusion Test (ID) for a period of 30 months. At the beginning the herd consisted of eight animals, where four of them showed clinical symptoms indicative for a MV-infection with positive serological results. The other 4 animals were negative. The herd increased in number by including the offspring and buying in other animals. During the time of 30 months only in one animal a seroconversion could be observed. In nine of 13 lambs borne of seropositive mothers colostral antibodies could be observed. By testing the colostrum of MV-seropositive mothers 6 of 7 animals showed precipitating antibodies. Positive sera showed average titers of 1:2 till 1:64, the highest titer was 1:512. On the postmortal examination of five serological positive animals which were killed because of dominant clinical symptoms, three of them showed MV-lesions partly superinfected with bacteria. In one sheep the diagnosis was pasteurellosis. On a further animal the clinical picture and the histologic results were indicative for the Visna-form of the disease.

[Neurologic symptoms in inhalation poisoning with metallic mercury]

Nineteen caisson workers had been exposed to metallic mercury vapours while digging tubes underneath the first district of Vienna (exposure between 470 and 2440 min; mean 1621 min). The blood mercury values on admission were between 29 and 166 micrograms/l (mean 75 +/- 34 micrograms/l). The main findings reported are clinical neurologic symptoms, psychic complaints, neurographic results and autonomic parameters (cardiovascular reflexes): 47% complained of headache and tiredness, 37% showed tremor and suffered from sleep disturbances, 26% showed hypersalivation, 16% changes in handwriting, and 11% slight dysarthria. The cardiovascular reflexes (autonomic parameters) were abnormal in 7 of 12 patients. On neurography the distal latency (median nerve) was pathologic in 47%, the distal latency (peroneal nerve) was pathologic in 26%, the antidromic sensory nerve conduction velocity (median nerve) was abnormal in 10%, the motor nerve conduction velocity, compound amplitude and vibratory threshold were normal.

A fluorescent antibody technique for identification of Mycoplasma hyopneumoniae colonies

Fluorescent antibody staining of Mycoplasma hyopneumoniae colonies is difficult because the colonies wash from the agar. Airdrying of the colonies grown on solid medium-overlayed glass microscope slides fixed the colonies in place, so that fluorescent antibody stain could be readily accomplished. Apparent loss or alteration of antigenicity did not result from the air-drying process. The technique is useful for the identification of M hyopneumoniae isolates.