Workload and stress in consultant medical microbiologists and virologists: a questionnaire survey

AIMS

To document demography, changing workload patterns, job satisfaction, morale, and prevalence of stress and psychological morbidity among UK consultant medical microbiologists and virologists.

METHOD

A questionnaire survey of all identified UK practising consultant medical microbiologists and virologists (n= 464).

RESULTS

Among 367 respondents (79%), there were 33 virologists and at least 89 single handed consultants. Over half the respondents (58%) were working a 1 : 1 or 1 : 2 on call rota during the week and a similar proportion (51%) at weekends. Of all consultants (including those working part time), 56% were working more than 48 hours weekly. Working more than 48 hours weekly, and being on call 1 : 1 or 1 : 2 at weekends, were both independently associated with increased psychological morbidity. Those on call 1 : 1 or 1 : 2 at weekends were also more likely to have low or very low morale. Female consultants were more likely to have higher stress scores. More than half of the respondents (208 of 363; 57%) were making active financial provision to retire early, and 198 of 363 (55%) did not intend to work beyond the age of 60.

CONCLUSIONS

The long hours worked by many consultant microbiologists and virologists are in breach of the European Working Time Directive and are associated with a higher degree of psychological morbidity. For most consultants, the frequency of on call commitments is demanding and job satisfaction and morale have deteriorated. Urgent action is needed, particularly to support those working more than 48 hours each week and those on call at weekends 1 : 1 or 1 : 2. However, a major expansion of the consultant establishment cannot be achieved rapidly, and will be slowed further if early retirements become more frequent.

Immunohistochemical detection of CD30 remains negative in nodular lymphocyte-predominant Hodgkin's disease using enhanced antigen retrieval

AIMS

The aims of this study were to confirm that CD30 is reproducibly negative in cases of nodular lymphocyte-predominant Hodgkin's disease (nLPHD), and its relationship to further antibody targets for the distinction of L&H cells from classical Hodgkin's and Reed-Sternberg cells.

METHODS AND RESULTS

We examined 16 cases of nLPHD from two centres in the UK to characterize immunohistochemically L&H cells for CD30, EMA, J-chain and Oct2, using different methods of antigen retrieval, antigen amplification and antigen detection systems. Two cases could not be stained with J-chain and Oct2. All cases were negative for CD30 following manual and automated staining. Only one case became positive for EMA after manual staining using tyramide amplification. J-chain and Oct2 were negative in all cases following manual staining. J-chain showed a positive result of variable degree in all but one case using automated Dako ChemMate amplification system staining. Oct2 demonstrated a positive, albeit variable, staining pattern in all cases following automated staining.

CONCLUSIONS

CD30 remains negative in L&H cells of nLPHD using enhanced antigen retrieval and can therefore reliably be used to distinguish nLPHD from classical Hodgkin's disease. The value of EMA in the diagnosis of nLPHD remains uncertain, as it does not reproducibly mark L&H cells, even after the use of enhanced antigen retrieval. J-chain and Oct2 appear to be useful markers in the diagnosis of nLPHD using enhanced immunostaining and should therefore be included in lymphoma panels. Automated enhanced staining, using standardized protocols, precoated slides and the full system of prepared reagents, further diminishes the occurrence of errors associated with manual staining, and thereby improves confidence and reliability in diagnosing nLPHD.

Sex, ethnicity, age and education effects on the Trail Making test in a sample of cocaine abusers

Sex, ethnicity, age and education effects on the Trail Making test (TMT), a test often used to for screen for cognitive impairment, were examined in a sample of cocaine abusers in drug abuse treatment programs. A mixed race sample of 5116 males and 2614 females was drawn from electronic files of data from the Drug Abuse Treatment Outcome Study (DATOS). The DATOS was a naturalistic, prospective cohort study that collected data from 1991-1993 in 96 programs in 11 cities in the United States. The number of cocaine/crack abuser scores available for analysis was 4306. Data were analyzed to determine the effects of sex, ethnicity, age and education variables on the two parts of the TMT in this large treatment sample of cocaine abusers. The variables of sex age, ethnicity and education were statistically significant for both parts A and B of the TMT. In addition, R-Square values for overall models were quite weak (A = .08, B = .11) suggesting that sex, ethnicity, age and education effects on the TMT, while clearly present, account for relatively little overall variance in terms of cocaine users TMT performance. These results are consistent with earlier research using a more heterogenous drug abuse treatment sample.

SB-236057-A: a selective 5-HT1B receptor inverse agonist

5-HT1B autoreceptors are involved in the control of extracellular 5-HT levels from both the terminal and cell body regions of serotonergic neurons. In this manuscript we review the pharmacological and pharmacokinetic data available for the selective and potent 5-HT1B receptor inverse agonist, SB-236057-A (1'-ethyl-5-(2'-methyl-4'-(5-methyl-1,3,4-oxadiazolyl-2-yl)biphenyl-4-carbonyl)-2,3,6,7-tetrahydrospiro (furo[2,3-f]indole-3,4'-piperidine) hydrochloride). SB 236057-A has been shown to have high affinity for human 5-HT1B receptors (pK(i) = 8.2) and displays 80 or more fold selectivity for the human 5-HT1B receptor over other 5-HT receptors and a range of additional receptors, ion channels and enzymes. In functional studies at human 5-HT1B receptors SB-236057-A displayed inverse agonism (pA(2) = 8.9) using [(35)S]GTPgammaS binding, and silent antagonism (pA(2) = 9.2) using cAMP accumulation. SB-236057-A also acted as an antagonist at the 5-HT terminal autoreceptor as measured by [3H]5-HT release from electrically stimulated guinea pig and human cortical slices. In the guinea pig, pharmacokinetic analysis demonstrated that SB-236057-A was bioavailable and according to in vivo pharmacodynamic assays it enters brain and has a long duration of action. Importantly no side effect liability was evident at relevant doses from anxiogenic, cardiovascular, sedative or migraine viewpoints. In vivo microdialysis studies demonstrated that SB-236057-A is an antagonist in the guinea pig cortex but has no effect on extracellular 5-HT levels per se. In contrast, SB-236057-A increased extracellular 5-HT levels in the guinea pig dentate gyrus. This increase in 5-HT release was comparable to that observed after 14 days of paroxetine administration. SB-236057-A has been a useful tool in confirming that, in either guinea pigs or humans, the terminal 5-HT autoreceptor is of the 5-HT1B subtype. It appears that acute 5-HT1B receptor blockade, by virtue of increased 5-HT release in the dentate gyrus, may provide a rapidly acting antidepressant.

Ligands for the investigation of 5-HT autoreceptor function

The existence of multiple 5-HT autoreceptors in the central nervous system is now firmly established and they have been pharmacologically identified as belonging to the 5-HT(1A), 5-HT(1B), and 5-HT(1D) receptor subtypes. In addition, 5-HT(1F), 5-HT(5A), and 5-HT(7) receptors remain as potential candidates for additional autoreceptors. The emergence of selective ligands, such as SB-224289 (5-HT(1B) receptor antagonist), BRL 15572 (5-HT(1D) receptor antagonist), GR 127935 (a mixed 5-HT(1B/1D) receptor antagonist), LY 334370 (5-HT(1F) receptor agonist), and SB-269970 (5-HT(7) receptor antagonist), has aided the characterisation of 5-HT autoreceptors and has highlighted the complexity of mechanisms which modulate the release of 5-HT.

Effect of Acute Biomechanical Changes on Corneal Curvature After Photokeratectomy

PURPOSE

Unintended hyperopic shift is a common yet poorly understood complication of phototherapeutic keratectomy (PTK) that raises fundamental questions about the etiology of corneal curvature change in PRK and LASIK. We investigated the relative contributions of ablation profile and peripheral stromal thickening to intraoperative PTK-induced central flattening, and propose a biomechanical model of the acute corneal response to central ablation.

METHODS

Fourteen de-epithelialized eye bank globes from seven donors underwent either broadbeam ablation (approximately 100-microm depth, no programmed dioptric change) or sham photoablation in paired-control fashion. Peripheral stromal thickness changes and the pattern of thickness loss across each ablation zone were evaluated by optical section image analysis as predictors of acute corneal flattening.

RESULTS

Relative to sham ablation, keratectomy caused significant anterior corneal flattening (-6.3+/-3.2 D, P = .002). Concomitant peripheral stromal thickening (+57+/-43 microm, P = .01) was a significant predictor of acute hyperopic shift (r = 0.68, P = .047). Ablation pattern bias did not consistently favor hyperopia and was a poor lone predictor of hyperopic shift.

CONCLUSIONS

Unintended keratectomy-induced hyperopic shift is replicable in a human donor model and is associated with significant thickening of the unablated peripheral stroma. This biomechanical response may have a considerable impact on early refractive outcomes in PTK, PRK, and LASIK.

Guided self-management and patient-directed follow-up of ulcerative colitis: a randomised trial

BACKGROUND

Ulcerative colitis is managed mainly in secondary care by regular outpatient reviews done by specialist clinicians. Alternatives would be to discharge patients to primary care or to provide open-access clinics, but neither of these options reduce patients' dependency on doctors or allow patients' involvement in disease management. We did a randomised controlled trial to assess an alternative to traditional outpatient care.

METHODS

We randomly assigned 203 patients with ulcerative colitis who were undergoing hospital follow-up to receive patient-centred self-management training and follow-up on request (intervention group), or normal treatment and follow-up (control group). The main outcome was the interval between relapse and treatment, and secondary outcomes were rates of primary and secondary care consultation, quality of life, and acceptability to patients. Analysis was by intention to treat.

FINDINGS

Intervention patients had relapses treated within a mean of 14.8 h (SD 19.1) compared with 49.6 h (65.1) in controls (difference 34.8 h [95% CI 16.4-60.2]). Furthermore, intervention patients compared with controls made significantly fewer visits to hospital (0.9 vs 2.9 per patient per year, difference 2.0 [1.6-2.7]) and to the primary-care physician (0.3 vs 0.9 per patient per year, difference 0.6 [0.2-1.1], p<0.006). Only two patients in the intervention group preferred traditional management. Health-related quality-of-life scores were unchanged in both groups.

INTERPRETATION

Self-management of ulcerative colitis accelerates treatment provision and reduces doctor visits, and does not increase morbidity. This approach could be used in long-term management of many other chronic diseases to improve health-service provision and use, and to reduce costs.

Systematic reviews of the effectiveness of day care for people with severe mental disorders: (1) acute day hospital versus admission; (2) vocational rehabilitation; (3) day hospital versus outpatient care

***ACUTE DAY HOSPITAL VERSUS ADMISSION FOR ACUTE PSYCHIATRIC DISORDERS***

BACKGROUND

Inpatient treatment is an expensive way of caring for people with acute psychiatric disorders. It has been proposed that many of those currently treated as inpatients could be cared for in acute psychiatric day hospitals.

OBJECTIVE

The aim of this review was to assess the effectiveness and feasibility of day hospital versus inpatient care for people with acute psychiatric disorders.

METHODS - STUDY SELECTION

Eligible studies were randomised controlled trials of day hospital versus inpatient care for people with acute psychiatric disorders. Studies were excluded if they were primarily concerned with elderly people, children, or patients with a diagnosis of organic brain disease or substance abuse. METHODS - DATA SOURCES: We searched the Cochrane Controlled Trials Register, MEDLINE, EMBASE, CINAHL, PsycLIT, and the reference lists of articles. Researchers were approached to identify unpublished studies. Trialists were asked to provide individual patient data. METHODS - DATA EXTRACTION: Data were extracted independently by two reviewers and cross-checked. METHODS - DATA SYNTHESIS: Relative risk (RR) and 95% confidence intervals (CIs) were calculated for dichotomous data. Weighted or standardised means were calculated for continuous data. Day hospital trials tend to present similar outcomes in slightly different formats, making it difficult to synthesise the data. Individual patient data were therefore sought so that outcomes could be re-analysed using a common format.

RESULTS

Nine trials met the inclusion criteria (involving 1568 randomised patients and 2268 assessed for suitability of day hospital treatment). Individual patient data were obtained for four trials (involving 594 people). A sensitivity analysis of combined data suggested that day hospital treatment was feasible for at worst 23.2% (n = 2268; 95% CI, 21.2 to 25.2) and at best 37.5% (n = 1768; 95% CI, 35.2 to 39.8) of those currently admitted to inpatient care. Individual patient data from three trials showed no difference in the number of days in hospital (combining day hospital days and inpatient days) between day hospital patients and controls (n = 465; weighted mean difference (WMD) = -0.38 days/ month; 95% CI, -1.32 to 0.55). However, compared with controls, patients randomised to day hospital care spent significantly more days in day hospital care (n = 265; WMD = 2.34 days/month; 95% CI, 1.97 to 2.70) and significantly fewer days in inpatient care (n = 265; WMD = -2.75 days/month; 95% CI, -3.63 to -1.87). There was no difference between readmission rates for day hospital and control patients (n = 667; RR = 0.91; 95% CI, 0.72 to 1.15). Individual patient data from three trials showed a significant time-treatment interaction, indicating a more rapid improvement in mental state (n = 407; c2 = 9.66; p = 0.002), but not social functioning (n = 295; c2 = 0.006; p = 0.941) amongst day hospital patients. Four of five trials demonstrated that day hospital care was cheaper than inpatient care (with overall cost reductions ranging from 20.9% to 36.9%).

CONCLUSIONS

Acute day hospitals are an attractive option in situations where demand for inpatient care is high and facilities exist that are suitable for conversion. They are a less attractive option when demand for inpatient care is low and where effective alternatives already exist. The interpretation of day hospital research would be enhanced if future trials made use of the common set of outcome measures used in this review. It is important to examine how acute day hospital care can be most effectively integrated into a modern community-based psychiatric service. ***VOCATIONAL REHABILITATION FOR PEOPLE WITH SEVERE MENTAL DISORDERS***

BACKGROUND

People who are disabled by severe mental disorders experience high rates of unemployment, but most want to work. Prevocational training (PVT) is the traditional approach to helping such people to return to work. PVT assumes that a period of preparation is required before those with a severe mental disorder can enter into competitive employment. Supported Employment (SEm) is a new approach that places clients in competitive employment without extended preparation. Both PVT and SEm are widely practised, but it is unclear which is the most effective.

OBJECTIVES

The overall objective of this review was to assess the effectiveness of PVT and SEm relative to each other and to standard care (in hospital or the community) for people with severe mental disorders. In addition, the review examined the effectiveness of: (1) special types of PVT ("clubhouse" model) and SEm (individual placement and support model); and (2) modifications for enhancing PVT (e.g. payment or psychological interventions).

METHODS - STUDY SELECTION

Eligible studies were randomised controlled trials (RCTs) examining the effectiveness of vocational rehabilitation approaches (PVT and SEm or modifications) for people of working age and suffering from a severe mental disorder. METHODS - DATA SOURCES: Relevant trials were identified from searches of the Cochrane Schizophrenia Group's specialised register, MEDLINE, EMBASE, CINAHL and PsycLIT, and the reference lists of all identified studies and review articles. Researchers who were active in the field were approached in order to identify unpublished studies. METHODS - DATA EXTRACTION: All data were extracted independently by two reviewers and cross-checked. Continuous data were excluded if they were collected by using an unpublished scale or were based on a subset of items from a scale. METHODS - DATA SYNTHESIS: For all comparisons, the primary outcome was the number of clients who were in competitive employment at various time points. Secondary outcomes were: other employment outcomes, clinical outcome and costs. The relative risk (RR) and number-needed-to-treat (NNT) were calculated for the relevant categorical outcomes. Continuous data were either presented as in the original trial reports or, where possible, combined across trials as a standardised mean difference score.

RESULTS

Eighteen RCTs of reasonable quality were identified: PVT versus hospital controls, three RCTs, n = 172; PVT versus community controls, five RCTs, n = 1204; modified PVT, four RCTs, n = 423; SEm versus community controls, one RCT, n = 256; and SEm versus PVT, five RCTs, n = 491). The main finding was that, on the primary outcome (number in competitive employment), SEm was significantly more effective than PVT at all time points (e.g. at 12 months, SEm 34% employed, PVT 12% employed; RR of not being in competitive employment = 0.76, 95% confidence interval 0.69 to 0.84, NNT = 4.5). Clients in SEm also earned more and worked more hours per month than those in PVT.

CONCLUSIONS

The main finding was that SEm was more effective than PVT for patients suffering from a severe mental disorder who wanted to work. There was no evidence that PVT was more effective than standard community care or hospital care. The implication of these findings is that people suffering from mental disorders who want to work should be offered the option of SEm. Commissioning agencies would be justified in encouraging vocational rehabilitation (VR) providers to develop more SEm schemes. From a research perspective, the cost-effectiveness of SEm should be examined in larger multicentre trials, both within and outside the USA. There is a case for countries outside the USA to survey their existing VR services to determine the extent to which the most effective interventions are being offered. ***DAY HOSPITAL VERSUS OUTPATIENT CARE FOR PATIENTS WITH PSYCHIATRIC DISORDERS***

BACKGROUND

This review considers the use of day hospitals as an alternative to outpatient care. Two typesof day hospital provision are covered: "day treatment programmes" and "day care centres". Day treatment programmes are day hospitals that are used to enhance the treatment of patients with anxiety or depressive disorders who have failed to respond to outpatient care. Day care centres are day hospitals that offer structured support to patients with long-term severe mental disorders who would otherwise be treated in an outpatient clinic.

OBJECTIVES

There were two objectives: first, to assess the effectiveness of day treatment programmes versus outpatient care for people with non-psychotic disorders; and, secondly, to assess the effectiveness of day care centres versus outpatient care for people with severe long-term disorders.

METHODS - STUDY SELECTION

Eligible studies were randomised controlled trials comparing day hospital care (either a day treatment programme or a day care centre) with outpatient care. Studies were ineligible if they were largely restricted to patients who were aged under 18 or over 65 years or who had a primary diagnosis of substance abuse or organic brain disorder. METHODS - DATA SOURCES: Relevant trials were identified from searches of the Cochrane Controlled Trials Register, MEDLINE, EMBASE, CINAHL, PsycLIT, and the reference lists of all identified studies and review articles. Researchers were approached to identify unpublished studies. Trialists were asked to provide individual patient data. METHODS - DATA EXTRACTION: All data were extracted independently by two reviewers and cross-checked. METHODS - DATA SYNTHESIS: Relative risks and 95% confidence intervals were calculated for dichotomous data. Standardised mean differences were calculated for continuous data.

RESULTS

There was evidence from two of the five trials identified suggesting that day treatment programmes were superior to continuing outpatient care in terms of improving psychiatric symptoms. There was no evidence to suggest that day treatment programmes were better or worse than outpatient care on any other clinical or social outcome variable or on costs. (ABSTRACT TRUNCATED)

Inflammatory endobronchial polyposis with bronchiectasis in cystic fibrosis

An unusual case of endobronchial polyposis associated with extensive bronchiectasis in the context of cystic fibrosis (CF) has been described. A 15-yr-old female patient with CF underwent partial pneumonectomy for extensive bronchiectasis and frequent infective pulmonary exacerbations. Cylindrical bronchiectasis with associated purulent bronchitis and bronchiolitis, together with inflammatory polyposis, was noted in the resected lung. To the best of the authors' knowledge, this is the first report of multiple endobronchial polyposis and may represent a rare complication of bronchiectasis in a patient with cystic fibrosis. On-going infection and the cellular composition of the polyps are discussed in relation to their possible aetiological relevance and relationship to upper respiratory tract polyps.

Demographic effects on the Trail Making Test in hallucinogen abusers

Demographic effects on the Trail Making test (TMT), a test often used for screening for cognitive impairment, were reexamined in a sample of hallucinogen abusers in drug abuse treatment programs. A sample was drawn from electronic files of data from the Drug Abuse Treatment outcome Study (DATOS). The DATOS was a naturalistic, prospective cohort study that collected data from 1991-1993 in 96 programs in 11 cities in the United States. The number of hallucinogen abusers' scores available for analysis were 128. Data were analyzed to determine the effects of sex, ethnicity, age and education variables on the two parts of the TMT in this large treatment sample of hallucinogen abusers. The variable of ethnicity was statistically significant for both parts A and B of the TMT and just at the edge of significance for age for part A. R-Square values for overall models were moderate (A = .30, B = .29) suggesting that demographic effects on the TMT account for a minority of overall variance in terms of hallucinogen abusers' TMT performance.

Sex, ethnicity, age and education effects on the Trail Making Test in a sample of heroin abusers

Sex, ethnicity, age and education effects on the Trail Making test (TMT), a test often used for screening for cognitive impairment, are examined in a sample of heroin abusers in drug abuse treatment programs. A mixed race sample was drawn from electronic files of data from the Drug Abuse Treatment outcome Study (DATOS). The DATOS was a naturalistic, prospective cohort study that collected data from 1991-1993 in 96 programs in 11 cities in the United States. The number of heroin abusers with TMT scores available for analysis was 1548. Data were analyzed to determine the effects of sex, ethnicity, age and education variables on the two parts of the TMT in this large treatment sample of heroin abusers. The variables of sex, age, ethnicity and education were statistically significant for both parts A and B of the TMT. Nonetheless, R-Square values for overall models were quite weak (A = .08, B = .13) suggesting that sex, ethnicity, age and education effects on the TMT, while clearly present, account for relatively little overall variance in terms of heroin users' TMT performance. These results are consistent with earlier research using a more heterogenous drug abuse treatment sample.

Retinal thickness measurements from optical coherence tomography using a Markov boundary model

We present a system for detecting retinal boundaries in optical coherence tomography (OCT) B-scans. OCT is a relatively new imaging modality giving cross-sectional images that are qualitatively similar to ultrasound. However, the axial resolution with OCT is much higher, on the order of 10 microm. Objective, quantitative measures of retinal thickness may be made from OCT images. Knowledge of retinal thickness is important in the evaluation and treatment of many ocular diseases. The boundary-detection system presented here uses a one-dimensional edge-detection kernel to yield edge primitives. These edge primitives are rated, selected, and organized to form a coherent boundary structure by use of a Markov model of retinal boundaries as detected by OCT. Qualitatively, the boundaries detected by the automated system generally agreed extremely well with the true retinal structure for the vast majority of OCT images. Only one of the 1450 evaluation images caused the algorithm to fail. A quantitative evaluation of the retinal boundaries was performed as well, using the clinical application of automatic retinal thickness determination. Retinal thickness measurements derived from the algorithm's results were compared with thickness measurements from manually corrected boundaries for 1450 test images. The algorithm's thickness measurements over a 1-mm region near the fovea differed from the corrected thickness measurements by less than 10 microm for 74% of the images and by less than 25 microm (10% of normal retinal thickness) for 98.4% of the images. These errors are near the machine's resolution limit and still well below clinical significance. Current, standard clinical practice involves a qualitative, visual assessment of retinal thickness. A robust, quantitatively accurate system such as ours can be expected to improve patient care.

Paraoxonase status in coronary heart disease: are activity and concentration more important than genotype?

Human serum paraoxonase (PON1) hydrolyzes oxidized lipids in low density lipoprotein (LDL) and could therefore retard the development of atherosclerosis. In keeping with this hypothesis, several case-control studies have shown a relationship between the presence of coronary heart disease (CHD) and polymorphisms at amino acid positions 55 and 192 of PON1, which we associated with a decreased capacity of PON1 to protect LDL against the accumulation of lipid peroxides, but some other studies have not. However, the PON1 polymorphisms are only 1 factor in determining the activity and concentration of the enzyme. Only 3 of the previous 18 studies directly determined PON1 activity and concentration. Therefore, we studied PON1 activity, concentration, and gene distribution in 417 subjects with angiographically proven CHD and in 282 control subjects. We found that PON1 activity and concentration were significantly lower in subjects with CHD than in control subjects (activity to paraoxon 122.8 [3.3 to 802.8] versus 214.6 [26.3 to 620.8] nmol. min(-1). mL(-1), P<0.001; concentration 71.6 [11.4 to 489.3] versus 89.1 [16.8 to 527.4] microg/mL, P<0.001). There were no differences in the PON1-55 and -192 polymorphisms or clusterin concentration between patients with CHD and control subjects. These results indicate that lower PON1 activity and concentration and, therefore, the reduced ability to prevent LDL lipid peroxidation may be more important in determining the presence of CHD than paraoxonase genetic polymorphisms.

Clustering of hepatotoxins based on mechanism of toxicity using gene expression profiles

Microarray technology, which allows one to quantitate the expression of thousands of genes simultaneously, has begun to have a major impact on many different areas of drug discovery and development. The question remains of whether microarray analysis and gene expression signature profiles can be applied to the field of toxicology. To date, there are very few published studies showing the use of microarrays in toxicology and important questions remain regarding the predictability and accuracy of applying gene expression profiles to toxicology. To begin to address these questions, we have treated rats with 15 different known hepatotoxins, including allyl alcohol, amiodarone, Aroclor 1254, arsenic, carbamazepine, carbon tetrachloride, diethylnitrosamine, dimethylformamide, diquat, etoposide, indomethacin, methapyrilene, methotrexate, monocrotaline, and 3-methylcholanthrene. These agents cause a variety of hepatocellular injuries including necrosis, DNA damage, cirrhosis, hypertrophy, and hepatic carcinoma. Gene expression analysis was done on RNA from the livers of treated rats and was compared against vehicle-treated controls. The gene expression results were clustered and compared to the histopathology findings and clinical chemistry values. Our results show strong correlation between the histopathology, clinical chemistry, and gene expression profiles induced by the agents. In addition, genes were identified whose regulation correlated strongly with effects on clinical chemistry parameters. Overall, the results suggest that microarray assays may prove to be a highly sensitive technique for safety screening of drug candidates and for the classification of environmental toxins.