Isolation, characterization, and experimental infection of Streptococcus gallolyticus subspecies pasteurianus from commercial turkeys with acute septicemia: a pilot study

Streptococcus gallolyticus (SG) is a Gram-positive cocci found as commensal gut flora in animals and humans. SG has emerged as a cause of disease in young poults between 1 and 3 wk of age. SG is associated with septicemia resulting in acute mortality with no premonitory signs in turkeys. Three SG isolates were obtained from clinical field cases of acute septicemia of commercial turkeys and used in three independent experiments. In Experiment 1, embryos were inoculated 25 d of embryogenesis with varying concentrations of SG1, SG2, or SG3. In Experiment 2, day of hatch, poults were inoculated with varying concentrations using different routes of administration of SG1, SG2, or SG3. In Experiment 3, day of hatch, poults were inoculated with only isolate SG1 using different paths. Poults were randomly selected for necropsy on d 8 and d 15 and sampled to collect spleen, heart, and liver for SG on d 21, the remaining poults were necropsied and cultured. Samples were plated on Columbia nalidixic acid and colistin agar (CNA) (40°C, 18-24 h). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) confirmed suspect colonies. Data were analyzed using the chi-square test of independence, testing all possible combinations to determine significance (P < 0.05). Weight data were subjected to ANOVA using JMP with significance (P < 0.05). No differences were found in BW or BWG on d 0, 8, 15, or 22. Splenomegaly, focal heart necrosis, and pericarditis were observed in all groups in experiments 1 through 3. In Experiment 3, only airsacculitis was observed in a negative control in separate isolation (P > 0.05). On d 21 of Experiment 3, increased (P < 0.05) recovery of SG from spleens were observed in co-housed negative controls, as well as poults challenged by oral gavage (P > 0.05 for d 7 and d 14). These results confirm numerous previous studies indicating that SG subsp. pasteurianus is a primary infectious microorganism that causes septicemia in young poults.

Evaluation of the impact of formaldehyde fumigation during the hatching phase on contamination in the hatch cabinet and early performance in broiler chickens

Commercial hatch cabinet environments promote replication of microorganisms. These pathogenic or apathogenic microorganisms may serve as pioneer colonizers of the gastrointestinal tract (GIT) of poultry. Some of these pioneer colonizers, such as Escherichia coli and Enterococcus spp., are opportunistic pathogens that lead to reduced performance in commercial poultry. Effective hatchery sanitation is imperative to limit contamination of naïve neonatal chicks and poults. Formaldehyde fumigation has been traditionally used to reduce the pathogen load in commercial hatch cabinets. To investigate potential alternatives to formaldehyde fumigation, models to mimic the microbial bloom in a laboratory setting must be utilized. The purpose of the present study was to evaluate the impact of a multispecies environmental challenge model (PM challenge) with and without formaldehyde fumigation during the hatching phase on early performance in broiler chicks. Three experiments were conducted to evaluate microbial contamination in the hatch cabinet environment (air samples, fluff samples), enteric colonization at day-of-hatch (DOH), and 7-day performance. In all experiments, significantly (P < 0.05) more gram-negative bacteria were recovered from the GIT at DOH in the PM challenge control group as compared to the nonchallenged control (NC) group and the formaldehyde-treated group (PM + F). There were no statistical differences in 7-day body weight gain or feed conversion ratio between the PM challenge control group, the NC group or the PM + F group. These data suggest this model could be utilized to evaluate alternatives to formaldehyde fumigation for controlling the microbial load during the hatching phase in a laboratory setting.

Development of an environmental contamination model to simulate the microbial bloom that occurs in commercial hatch cabinets

Microbial blooms that emerge in commercial hatch cabinets consist of apathogenic and pathogenic microorganisms, including Escherichia coli, Enterococcus faecalis, and Aspergillus fumigatus. Objectives of the present study included the development of a multipathogen contamination model to mimic commercial conditions and optimization of sampling methods to quantify bacterial or fungal presence within the hatch cabinet. The pathogen challenge mix (PM) was recreated from select bacterial or fungal isolates recovered from an egg homogenate (EH) derived from the contents of infertile eggs and late embryonic mortalities. Isolates selected for PM included Enterococcus faecalis (∼10⁸ CFU/egg), Staphylococcus aureus (∼10⁷ CFU/egg), Staphylococcus chromogenes (∼10⁷ CFU/egg), Aspergillus fumigatus (∼10⁶ spores/egg), and 2 Escherichia coli (∼10⁸ CFU/egg) isolates. Challenge (100 μL of PM or EH) was administered using a sterile loop to a 28 mm area on the blunt end of the eggshell at day 19 of embryogenesis (DOE). In 3 experiments, microbiological data were collected from environmental hatcher samples (open-agar plate method), fluff samples, postmortem whole-body chick rinse samples, and gastrointestinal tract (GIT) samples to evaluate select bacteria and fungi circulating within the hatch cabinet and colonization of GIT. Cumulative bacterial and fungal recovery from the PM hatching environment from DOE20 to hatch was higher than the nonchallenged group (NC) and EH group at ∼860 and ∼1,730 CFU, respectively. Bacterial recovery from GIT, fluff, and chick rinse samples were similar for the PM and EH group in Exp. 1. However, Aspergillus fumigatus recovery from fluff and chick rinse samples for the PM group was significantly (P < 0.001) higher than the NC and EH group. In Exp. 2 and 3, PM challenge significantly (P < 0.05) increased Gram-negative bacterial recovery from the GIT, fluff and chick rinse samples compared to both the NC and EH group. These data suggest this innovative multispecies environmental contamination model using PM could be utilized to evaluate strategies to mitigate microbial contamination in commercial hatch cabinets in a laboratory setting.

Binding of IgG and other proteins to microfilters

We evaluated 10 microfilters for their ability to filter diluted sera without removing immunoglobulins (Ig) G, A, and M, albumin, and transferrin. In general, filters containing cellulose nitrate remove IgG from solution, the amount adsorbed being proportional to the IgG concentration in the solution. With some sera we noted IgA and IgM adsorption to cellulose-nitrate-containing filters, but there was no significant adsorption of albumin or transferrin to any of the filters. We also found that cellulose-nitrate filters adsorbed IgG from antiserum, with consequent loss of titre as seen in a nephelometric assay. Adsorption of IgG was not seen if the filters were prewashed with polyethylene glycol or if the antisera contained polyethylene glycol. With a sufficiently large antibody excess in the nephelometric assay, this loss of titre through filtration becomes undetectable.

Psychometric evaluation of the Beck Depression Inventory in adults with social anxiety disorder

Although the Beck Depression Inventory (BDI) is commonly used to assess levels of depressive symptoms in socially anxious adults, its psychometric properties in this context have never been formally examined. Therefore, we examined the psychometrics of the BDI in a sample of adults with a principal diagnosis of social anxiety disorder (N = 113). The BDI exhibited good internal consistency and re-test reliability. It also correlated significantly more strongly with other measures of depression than with measures of either social or non-social anxiety. Thus, the BDI appears to be a valid tool for the assessment of depressive symptoms in adults with social anxiety disorder.

The Liebowitz Social Anxiety Scale: a comparison of the psychometric properties of self-report and clinician-administered formats

BACKGROUND

The clinician-administered version of the Liebowitz Social Anxiety Scale (LSAS-CA) is a commonly used assessment device for the evaluation of social anxiety disorder and has been shown to have strong psychometric characteristics. Because of its apparently straightforward rating format and potential savings in time and effort, interest in the use of the LSAS as a self-report (LSAS-SR) measure has increased, and the LSAS-SR has been used in a number of studies. However, the psychometric properties of the LSAS-SR have not been well established.

METHODS

This study examined the psychometric properties of the LSAS-SR in comparison to the LSAS-CA in a sample of 99 individuals with a primary diagnosis of social anxiety disorder and 53 individuals with no current psychiatric disorder.

RESULTS

There was little difference between the two versions of the LSAS on any scale or subscale score. Both forms were internally consistent and the subscale intercorrelations for the two forms were essentially identical. Correlations of each LSAS-SR index with its LSAS-CA counterpart were all highly significant. Finally, the convergent and discriminant validity of the two forms of the LSAS was shown to be strong.

CONCLUSION

Results of this study suggest that the self-report version of the LSAS compares well to the clinician-administered version and may be validly employed in the assessment of social anxiety disorder.

Distinguishing obsessive features and worries: the role of thought-action fusion

Obsessions are a key feature of obsessive-compulsive disorder (OCD), and chronic worry is the cardinal feature of generalized anxiety disorder (GAD). However, these two cognitive processes are conceptually very similar, and there is a need to determine how they differ. Recent studies have attempted to identify cognitive processes that may be differentially related to obsessive features and worry. In the current study we proposed that (1) obsessive features and worry could be differentiated and that (2) a measure of the cognitive process thought-action fusion would distinguish between obsessive features and worry, being strongly related to obsessive features after controlling for the effects of worry. These hypotheses were supported in a sample of 173 undergraduate students. Thought-action fusion may be a valuable construct in differentiating between obsessive features and worry.

Effects of varying levels of anxiety within social situations: relationship to memory perspective and attributions in social phobia

Cognitive-behavioral theorists (Clark & Wells, 1995: Clark, D. M. & Wells, A. (1995). A cognitive model of social phobia. In R. G. Heimberg, M. R. Liebowitz, D. A. Hope, & F. R. Schneier (Eds.), Social phobia: Diagnosis, assessment, and treatment (pp. 69-93). New York: Guilford Press; Rapee & Heimberg, 1997: Rapee, R. M., & Heimberg, R. G. (1997). A cognitive-behavioral model of anxiety in social phobia. Behaviour Research and Therapy, 35, 741-756.) propose that individuals with social phobia form mental images of themselves as if from an external point of view. Research by Wells and colleagues has shown that, when recalling anxiety-provoking social situations, individuals with social phobia are more likely to take an observer perspective (seeing oneself as if from an external point of view) whereas control subjects are more likely to take a field perspective (as if looking out through one's own eyes). Furthermore, this pattern is specific to social events, as both groups recall non-social events from a field perspective (see Wells, Clark & Ahmad, 1998: Wells, A., Clark, D. M., & Ahmad, S. (1998). How do I look with my minds eye: perspective taking in social phobic imagery. Behaviour Research and Therapy, 36, 631-634; Wells & Papageorigou, 1999: Wells, A. & Papageorgiou, C. (1999). The observer perspective: Biased imagery in social phobia, agoraphobia, and blood/injury phobia. Behaviour Research and Therapy, 37, 653-658). In the current study, individuals with social phobia took more of an observer perspective than non-anxious controls when recalling high anxiety social situations. However, both groups took a predominantly field perspective for memories of medium or low anxiety social situations. As memory perspective has also been shown to be related to causal attributions, we examined this relationship in our sample. Memories of low, medium, and high anxiety social situations were differentially related to attributions for each group. Patients' attributions for their performance became more internal, stable, and global as the anxiety level of the situation increased, while the attributions of control subjects showed the opposite pattern.

The effect of practice on recall of emotional information in individuals with generalized social phobia

Understanding memory processes in social anxiety is important because these individuals often report negative memories of anxiety-provoking situations and because of the recent emphasis on learning and memory in models of anxiety. The authors examined the effect of learning on memory for negative social, positive social, and nonsocial information using the retrieval-induced forgetting paradigm in individuals with generalized social phobia (GSPs) and in nonanxious controls (NACs). Words were presented in 1 of 3 practice conditions: practiced words from a practiced category, unpracticed words from a practiced category, and unpracticed words from an unpracticed category. GSPs and NACs showed the same patterns of memory for practice categories for positive social and nonsocial words. However, for negative social words, GSPs benefited less from practice and were hurt less from the effect of practicing competing negative social information than were NACs. This pattern of processing may hamper GSPs' learning of, and habituation to, negative social information.

Implicit memory bias for threat-relevant information in individuals with generalized social phobia

The authors used a noise judgment task to investigate implicit memory bias for threat in individuals with generalized social phobia (GSP). Participants first heard neutral sentences (e.g., "The manual tells you how to set up the tent.") and social-threat sentences (e.g., "The classmate asks you to go for drinks."). Implicit memory for these sentences was then tested by asking participants to rate the volume of noise accompanying the presentation of these "old" sentences intermixed with "new" sentences that had not been previously presented. Implicit memory for old sentences is revealed when participants rate the noise accompanying old sentences as less loud than the noise accompanying new sentences. Those with GSP demonstrated an implicit memory bias for social-threat sentences, whereas controls did not. This differential priming effect suggests that information about threat may be automatically accessed in GSP.

The effect of practice on recall of emotional information in individuals with generalized social phobia

Understanding memory processes in social anxiety is important because these individuals often report negative memories of anxiety-provoking situations and because of the recent emphasis on learning and memory in models of anxiety. The authors examined the effect of learning on memory for negative social, positive social, and nonsocial information using the retrieval-induced forgetting paradigm in individuals with generalized social phobia (GSPs) and in nonanxious controls (NACs). Words were presented in 1 of 3 practice conditions: practiced words from a practiced category, unpracticed words from a practiced category, and unpracticed words from an unpracticed category. GSPs and NACs showed the same patterns of memory for practice categories for positive social and nonsocial words. However, for negative social words, GSPs benefited less from practice and were hurt less from the effect of practicing competing negative social information than were NACs. This pattern of processing may hamper GSPs' learning of, and habituation to, negative social information.

Implicit memory bias for threat-relevant information in individuals with generalized social phobia

The authors used a noise judgment task to investigate implicit memory bias for threat in individuals with generalized social phobia (GSP). Participants first heard neutral sentences (e.g., "The manual tells you how to set up the tent.") and social-threat sentences (e.g., "The classmate asks you to go for drinks."). Implicit memory for these sentences was then tested by asking participants to rate the volume of noise accompanying the presentation of these "old" sentences intermixed with "new" sentences that had not been previously presented. Implicit memory for old sentences is revealed when participants rate the noise accompanying old sentences as less loud than the noise accompanying new sentences. Those with GSP demonstrated an implicit memory bias for social-threat sentences, whereas controls did not. This differential priming effect suggests that information about threat may be automatically accessed in GSP.

An empirical approach to subtype identification in individuals with social phobia

BACKGROUND

The present study used cluster analysis procedures to identify empirically subgroups of patients with social phobia in a large clinical sample.

METHOD

The Liebowitz Social Anxiety Scale (LSAS) was administered to 382 patients from several studies of the treatment of social phobia. LSAS fear ratings were summed into four subscale scores (social interaction, public speaking, observation by others, eating and drinking in public) based on a previous factor analytical study of the LSAS. In order to produce a stable and robust solution, these factor scores were submitted to a two-stage clustering procedure consisting of an agglomerative-hierarchical clustering method followed by an iterative non-hierarchical clustering method.

RESULTS

Three patient subgroups were identified based on their pattern of feared social situations on the LSAS. These groups were labelled: (1) pervasive social anxiety; (2) moderate social interaction anxiety; and (3) dominant public speaking anxiety. Clusters differed significantly on age and age of social phobia onset, as well as on measures of social anxiety, general anxiety and depressive symptomatology. Clusters also differed in the percentage of assigned patients who met criteria for the generalized subtype of social phobia and avoidant personality disorder.

CONCLUSIONS

The results provide empirical support for the existence of three subgroups in a clinical sample of individuals with social phobia and contribute to the growing evidence for the heterogeneity of social phobia. Further study of the conceptual, clinical and aetiological significance of these subgroups is needed.

Patterns of anxious arousal during exposure to feared situations in individuals with social phobia

Behavioral assessment tests (BATs) are commonly used in studies of social phobia (SP). While previous studies have examined subjective anxiety during BATs, they have usually reported only mean or peak ratings. The current study examined whether there are different patterns of anxious arousal in anticipation of, and during exposure to, feared situations among individuals seeking treatment for SP (N = 153). A four cluster solution was judged to best describe the data, and the four clusters were labeled 'high anxiety,' 'increasing/high anxiety', 'moderate anxiety' and 'mild anxiety'. Before treatment, the cluster groups did not differ on person characteristics, subtype of social phobia, or levels of depressive symptoms. However, they did differ in terms of the severity of social phobia symptoms and the emotional valence of thoughts reported at the conclusion of the BAT. While members of all clusters benefited from cognitive-behavioral group therapy for social phobia, the clusters showed some differential response in amount of symptom reduction and likelihood of continuing to meet diagnostic criteria following treatment. The different emotional experiences of clients in the various clusters are explored and implications for cognitive-behavioral therapy are proposed. Finally, limitations of this study and future directions are discussed.

Negative interpretation bias in social phobia

We examined the hypothesis that, compared to non-anxious controls (NACs) and individuals with other anxiety disorders (e.g., individuals with obsessive compulsive disorder; OCs), individuals with generalized social phobia (GSPs) would tend to interpret ambiguous social scenarios as negative when provided with various alternative interpretations. Participants were presented with 22 ambiguous scenarios each followed by three possible interpretations: positive, negative, and neutral. Fifteen scenarios were socially relevant and the remaining 7 were nonsocially relevant. Participants were asked to rank order the three interpretations according to the likelihood that each would come to their mind and to a 'typical person's' mind in similar situations. Results revealed that GSPs (but not NACs or OCs) tended to choose a negative interpretation for ambiguous social scenarios even when a positive interpretation was available. This bias was specific to self-relevant scenarios. These results support the hypothesis that a specific negative interpretation bias may be involved in the maintenance of social phobia.

Automatic activation and strategic avoidance of threat-relevant information in social phobia

The authors examined the hypothesis that abnormalities in activation and inhibition of threat-relevant information may account for information-processing biases in social anxiety. Individuals with generalized social phobia (GSP) and nonanxious controls were presented with sentences ending in homographs and in nonhomographs and were asked to make decisions about a cue word that followed each sentence. Half of the homographs had a social-threat implication. Longer response latency to make decisions about sentences ending in homographs compared with sentences ending in nonhomographs is thought to reflect activation of the inappropriate meaning of the homographs. Results revealed that GSPs showed initial activation of inappropriate meanings of socially relevant homographs followed by later inhibition of these meanings. These findings are consistent with a vigilance-avoidance model of information processing of threat-relevant information in social phobia.

Automatic activation and strategic avoidance of threat-relevant information in social phobia

The authors examined the hypothesis that abnormalities in activation and inhibition of threat-relevant information may account for information-processing biases in social anxiety. Individuals with generalized social phobia (GSP) and nonanxious controls were presented with sentences ending in homographs and in nonhomographs and were asked to make decisions about a cue word that followed each sentence. Half of the homographs had a social-threat implication. Longer response latency to make decisions about sentences ending in homographs compared with sentences ending in nonhomographs is thought to reflect activation of the inappropriate meaning of the homographs. Results revealed that GSPs showed initial activation of inappropriate meanings of socially relevant homographs followed by later inhibition of these meanings. These findings are consistent with a vigilance-avoidance model of information processing of threat-relevant information in social phobia.

Cognitive-behavioral treatment of pediatric obsessive-compulsive disorder: an open clinical trial

OBJECTIVE

The purpose of this open clinical trial was to examine the efficacy of cognitive-behavioral treatment involving exposure and ritual prevention for pediatric obsessive-compulsive disorder (OCD).

METHOD

Children and adolescents with diagnosed OCD (N = 14) received cognitive-behavioral treatment, seven patients received intensive treatment (mean = 18 sessions over 1 month) and seven received weekly treatment (mean = 16 sessions over 4 months). Eight of these patients received concurrent treatment with serotonin reuptake inhibitors and six received cognitive-behavioral treatment alone. Outcome was assessed via interviewer ratings on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), Obsessive Compulsive Rating Scales for Main Fear and Main Ritual, and Hamilton Depression Rating Scale.

RESULTS

Cognitive-behavioral treatment was effective in ameliorating OCD symptoms. Twelve of the 14 patients were at least 50% improved over pretreatment Y-BOCS severity, and the vast majority remained improved at follow-up; mean reduction in Y-BOCS was 67% at posttreatment and 62% at follow-up (mean time to follow-up = 9 months).

CONCLUSIONS

Results suggest that cognitive-behavioral treatment by exposure and ritual prevention is effective for pediatric OCD. Controlled studies with random assignment to conditions are warranted to evaluate the relative efficacy of cognitive-behavioral pharmacological, and combined treatments.

Rescreening of a group at high risk for colorectal neoplasia using immunochemical tests for faecal occult blood

The results of a screening programme for colorectal neoplasia in a high risk group using an immunochemical test for blood has been reported recently. This test is known as the faecal human haemoglobin (FHH) test. This paper reports the results of rescreening this group after an interval of 1-2 years. The FHH test was compared with a paper disc method. All individuals with positive tests were investigated and those with negative tests were offered investigation. The results confirm the value of the FHH test in screening a high risk group: 19 individuals in 1,153 participants were found to have a significant neoplasm (1.6%). The predictive value of the test for a significant neoplasm was 42%. A false negative rate of 2.6% was found, all lesions being benign. It appears to be more reliable than the paper disc method but the differences do not reach statistical significance. The FHH test is recommended for screening the general population over the age of 40 years, with rescreening annually.

Evaluation of an immunochemical test for faecal occult blood in screening for colorectal neoplasia in a high risk group

A group of 1615 asymptomatic individuals presumed to be at increased risk of colorectal neoplasia were selected as the study group. All were tested by an immunochemical test for faecal occult blood. In the second half of the study, individuals who were occult blood negative were offered colonoscopy. Ninety-nine individuals (6.1%) returned stools which were occult blood positive. Investigation by full colonoscopy was possible in 90 cases, revealing nine patients (10%) with invasive cancers, four patients (4.4%) with carcinomata in situ, and 36 patients (40%) with adenomata. Non-neoplastic pathology capable of producing occult blood positive stools was found in 31 individuals (34.4%). No pathology was found in 10 instances (11.1%). Of the 53 occult blood negative subjects who underwent colonoscopy, eight were found to have adenomata. Only one of these was larger than 5 mm in diameter (18 mm). No carcinomata were found. The site within the large bowel of the tumour did not appear to significantly affect the occult blood status of the faeces but the size of the tumours detected suggests that the presence of blood within the stool is more likely to be associated with larger lesions. The frequency of detection of both carcinomata and adenomata was greatest in individuals who had a past history of colorectal neoplasia. The individual cost of this immunochemical test is nominal. The high diagnostic yield and low false positive and negative rates suggest that case follow-up, surveillance, or screening utilizing this test is justified.

An assessment of an immunochemical test for human haemoglobin in the detection of colonic polyps

It is now widely accepted that malignant tumours of the colon and rectum almost invariably arise from pre-existing adenomatous polyps. If such polyps could be detected and removed colonoscopically before they become malignant, theoretically the incidence of invasive colorectal cancer could be dramatically reduced. The purpose of this study was to determine whether an immunochemical test for faecal occult blood would identify patients with benign colonic polyps. The faecal samples from 121 patients scheduled to undergo colonoscopy were tested by our immunochemical method and the Hemoccult II test. There were nine patients who had malignant colorectal tumours. These were excluded from this study. Twenty-nine were found to have colonic polyps. Fifteen of these had one or more faecal samples which were positive by the immunochemical test. In contrast, there was only one patient who had a positive Hemoccult II test. Fourteen of the remaining 83 patients had positive immunochemical tests. The findings on colonoscopy provided satisfactory explanations in all these cases. Polyps of all sizes and histological type were associated with positive immunochemical tests. It is concluded that the immunochemical test has sufficiently high sensitivity for colonic polyps to make feasible the screening of patients at high risk of developing colonic cancer.

Albumin I.M.V.S.: a variant detected by a Bromcresol Green dye binding method

A unique variant of human albumin was discovered in a family following routine multiple biochemical analysis. Their sera demonstrated increased Bromcresol Green (BCG) dye binding under certain reaction conditions (excess amounts of the detergent Pegosperse in the presence of Merthiolate). This effect was also seen with a structurally similar dye, Bromcresol Purple (BCP). The variant sera also showed an altered pattern of BCG dye binding (in the presence of Merthiolate and excess Pegosperse) compared to normal sera when the temperature or the pH of the dye reagent was changed. Decreased binding of the dye 2-(4'-hydroxybenzeneazo)benzoic acid (HABA) was also noted. Similar findings were observed in six other patients over a period of 21 months. Column chromatography of the variant sera on a DEAE-Sepharose column separated the albumin into two fractions, one showing normal dye binding properties, the other showing the more extreme pattern of dye binding seen for the whole variant serum.

Evaluation of an immunological test for occult bleeding from colorectal neoplasia

A study to determine the reliability of a recently described test, the faecal human haemoglobin test (FHH), specific for human blood, in the detection of colorectal neoplasia, is reported. All of nineteen patients with proven cancers studied were shown to have detectable blood in the stools. Three of five patients with polyps in this series also had detectable blood in the stools by this test. Although three of nineteen control subjects had positive tests, two of these were subsequently found to have bleeding sites, and the third was normal on follow up some weeks later. The findings are discussed in relation to the Hemoccult II (H-O) test results obtained in these subjects, and the implications for the possible future role for this test in screening for colorectal neoplasia.

Binding of IgG and other proteins to microfilters

We evaluated 10 microfilters for their ability to filter diluted sera without removing immunoglobulins (Ig) G, A, and M, albumin, and transferrin. In general, filters containing cellulose nitrate remove IgG from solution, the amount adsorbed being proportional to the IgG concentration in the solution. With some sera we noted IgA and IgM adsorption to cellulose-nitrate-containing filters, but there was no significant adsorption of albumin or transferrin to any of the filters. We also found that cellulose-nitrate filters adsorbed IgG from antiserum, with consequent loss of titre as seen in a nephelometric assay. Adsorption of IgG was not seen if the filters were prewashed with polyethylene glycol or if the antisera contained polyethylene glycol. With a sufficiently large antibody excess in the nephelometric assay, this loss of titre through filtration becomes undetectable.

Binding of IgG and other proteins to microfilters

We evaluated 10 microfilters for their ability to filter diluted sera without removing immunoglobulins (Ig) G, A, and M, albumin, and transferrin. In general, filters containing cellulose nitrate remove IgG from solution, the amount adsorbed being proportional to the IgG concentration in the solution. With some sera we noted IgA and IgM adsorption to cellulose-nitrate-containing filters, but there was no significant adsorption of albumin or transferrin to any of the filters. We also found that cellulose-nitrate filters adsorbed IgG from antiserum, with consequent loss of titre as seen in a nephelometric assay. Adsorption of IgG was not seen if the filters were prewashed with polyethylene glycol or if the antisera contained polyethylene glycol. With a sufficiently large antibody excess in the nephelometric assay, this loss of titre through filtration becomes undetectable.

Evaluation of two commercially available laser nephelometers and their recommended methods for measurement of serum immunoglobulin G

The Hyland and Behring laser nephelometer systems for assay of specific proteins are described. Immunoglobulin G was measured to assess the overall performance of the two systems. Intra-batch precision figures were comparable to those for the radial immunodiffusion method run routinely in our laboratory. There was no significant interference from turbid or lipemic specimens. Accuracy, ease of instrument operation, standard curve stability, linearity, and accessory equipment are discussed. Immunoglobulin G is measured rapidly, accurately, and precisely by either system.

Evaluation of two commercially available laser nephelometers and their recommended methods for measurement of serum immunoglobulin G

The Hyland and Behring laser nephelometer systems for assay of specific proteins are described. Immunoglobulin G was measured to assess the overall performance of the two systems. Intra-batch precision figures were comparable to those for the radial immunodiffusion method run routinely in our laboratory. There was no significant interference from turbid or lipemic specimens. Accuracy, ease of instrument operation, standard curve stability, linearity, and accessory equipment are discussed. Immunoglobulin G is measured rapidly, accurately, and precisely by either system.

Alpha1-fetoprotein in the diagnosis of hepatoma: statistical and cost benefit aspects

A rational comparison of different serum concentrations of alpha1-fetoprotein (S-AFP) in the diagnosis of hepatoma must be made. We took data on the sensitivity and specificity of different diagnostic S-AFP concentrations from the literature and evaluated them statistically and by Bayesian analysis. In our patients (hepatoma prevalence 0.028) a sensitive diagnostic concentration (30-50 ng/ml) will misdiagnose hepatoma so often that a positive test will indicate hepatoma in only 10% of cases. A positive test at a specific diagnostic concentration (500 ng/ml) indicates hepatoma in 100% of cases and is preferable in terms of cost benefit. Although the lower concentration will diagnose a larger proportion of patients with hepatoma (74% compared with 59%) the 'costs' of excluding false positives are considerable (A$2545 per extra case with 2.5% of patients suffering significant morbidity). In western societies, where the prevalence of hepatoma is low, a higher, less sensitive but more specific diagnostic S-AFP concentration is appropriate.