Gout, Hyperuricaemia and Crystal-Associated Disease Network (G-CAN) consensus statement regarding labels and definitions of disease states of gout

OBJECTIVE

There is a lack of standardisation in the terminology used to describe gout. The aim of this project was to develop a consensus statement describing the recommended nomenclature for disease states of gout.

METHODS

A content analysis of gout-related articles from rheumatology and general internal medicine journals published over a 5-year period identified potential disease states and the labels commonly assigned to them. Based on these findings, experts in gout were invited to participate in a Delphi exercise and face-to-face consensus meeting to reach agreement on disease state labels and definitions.

RESULTS

The content analysis identified 13 unique disease states and a total of 63 unique labels. The Delphi exercise (n=76 respondents) and face-to-face meeting (n=35 attendees) established consensus agreement for eight disease state labels and definitions. The agreed labels were as follows: 'asymptomatic hyperuricaemia', 'asymptomatic monosodium urate crystal deposition', 'asymptomatic hyperuricaemia with monosodium urate crystal deposition', 'gout', 'tophaceous gout', 'erosive gout', 'first gout flare' and 'recurrent gout flares'. There was consensus agreement that the label 'gout' should be restricted to current or prior clinically evident disease caused by monosodium urate crystal deposition (gout flare, chronic gouty arthritis or subcutaneous tophus).

CONCLUSION

Consensus agreement has been established for the labels and definitions of eight gout disease states, including 'gout' itself. The Gout, Hyperuricaemia and Crystal-Associated Disease Network recommends the use of these labels when describing disease states of gout in research and clinical practice.

Is lupus a syndrome or a disease?

Does it matter whether we call lupus a disease or a syndrome? Because both conditions can be rigorously defined, this has little effect on uniformity of entry criteria for clinical trials. However, because diseases are the product of a single pathophysiologic mechanism, and syndromes are not, whether lupus is a disease or a syndrome does have broad ramifications. For example, looking for the "cause" or the "cure" for lupus involves a disease-specific conceptual framework, whereas, for syndromes we investigate risk factors and treatment modalities. On the basis of current laboratory data, we contend that lupus is a syndrome and only has candidate status as a disease. This helps to explain heterogeneity in results of studies of therapeutic agents and laboratory investigations of etiology. Patients, funding organizations, and lay support groups need to be aware of this distinction to reduce unrealistic expectations.

High-sensitivity C-reactive protein and erythrocyte sedimentation rate in systemic lupus erythematosus

Levels of C-reactive protein (CRP) have been shown to rise in acute illnesses such as infections and some autoimmune diseases, but not in flares of systemic lupus erythematosus (SLE). Our goal was to investigate the high-sensitivity CRP (hsCRP) response to infection versus disease flare in patients with SLE, and to compare this with the erythrocyte sedimentation rate (ESR) response in these patients. We aimed to determine the hsCRP level that distinguishes between infection and flare in SLE, and investigated the correlation between hsCRP and organ involvement in SLE. We reviewed electronic medical records of all patients with SLE admitted to Cedars Sinai Medical Center between 28 August 2001 and 27 April 2008. Patients were divided into three groups based on the reason for hospitalization: 1) lupus flare; 2) active infection; and 3) both lupus flare and active infection. Data were collected on patient demographics, medication use, microbial culture results, organ involvement in lupus flare, ESR and CRP levels. Data were collected on 85 eligible patients, of whom 54 had a lupus flare, 22 had active infection and eight had both. While the ESR levels did not differ significantly between patients with disease flare and active infection, the hsCRP level was significantly lower in the lupus flare group than in the infection group. Most patients in the lupus flare group who had a significantly high hsCRP level had serositis. We found that at a cut-off of above 5 mg/dl, hsCRP level was correlated with infection with a specificity of 80%. At a cut-off of above 6 mg/dl, hsCRP correlated with infection with a specificity of 84%. hsCRP level was found to be significantly higher in patients with pulmonary involvement than without. hsCRP levels are significantly lower in SLE patients with disease flare than in those with active infection. Elevated hsCRP levels can be used as a predictor of active infection in SLE patients with a high specificity. We review the relationship between IL-6 and hsCRP production in lupus patients.

Usage of intra-articular corticosteroid injections for the treatment of juvenile idiopathic arthritis: a survey of pediatric rheumatologists in the United States and Canada

OBJECTIVE

To characterize the current usage of intra-articular corticosteroid injections (IACI) by pediatric rheumatologists and the perceived disadvantages of and obstacles to IACI therapy.

METHODS

We mailed a 32-item questionnaire to pediatric rheumatologists in the United States and Canada (n=201) to assess treatment strategies for the initial treatment of monoarthritis of the knee in juvenile idiopathic arthritis (JIA). Information regarding the usage of IACI for all patients with JIA and physicians' perceptions of IACI therapy was obtained. Respondents were dichotomized into those who performed frequent pediatric IACI (greater than 50 IACI in the last 12 months) and those who did not.

RESULTS

One hundred and twenty-nine (64%) completed questionnaires were returned. IACI were recommended as one therapy for JIA by 99% of respondents, and 90% personally perform IACI. Frequent IACI were performed by 22%, and 15% had performed greater than 10 IACI in a single pediatric patient at one time. Those who did not perform frequent IACI were more likely to report concern about the pain of the procedure, the availability of nursing support, and their own comfort with performing the procedure; they were less likely to have performed greater than 20 pediatric IACI during fellowship training and evaluated fewer clinic patients per week.

CONCLUSION

IACI are essentially universally recommended in the treatment regimen for JIA. However, there are differences in the usage of IACI among pediatric rheumatologists. The frequency of IACI use is associated with different perceptions of and training received in IACI therapy.

Modeling therapeutic strategies in rheumatoid arthritis: use of decision analysis and Markov models

OBJECTIVE

The management of patients with rheumatoid arthritis (RA) is controversial, with a number of different proposed treatment strategies based on different conceptions of the natural history of the disease and different interpretations of the efficacy and effectiveness of the drugs used for treatment. We attempted to develop a theoretical framework to assess the effectiveness of different treatment regimens for RA.

METHODS

We used decision analysis to structure the problem of comparing sequential monotherapy to a combination strategy. Subsequently, we used 3 different estimates of drug effectiveness: one from expert rheumatologists; a metaanalysis; and a recent nationwide survey of American rheumatologists, in a Markov model. Last, we utilized published duration of therapy data to model drug treatment over time.

RESULTS

Estimates of drug effectiveness differed substantially among rheumatologists, but regardless of the estimates and the treatment strategy used, the model predicted over 90% of patients improved by the 3rd drug trial. Over time, treatment patterns in our model resemble the "sawtooth" pattern previously observed.

CONCLUSION

Treatment strategies in RA are difficult to model because of uncertainty in both the structure of the model and the data needed to perform the analysis. These models tend to overestimate the effectiveness of drug sequences because of nonindependence between therapies, probably due to sequence effects, a change in responsiveness over time, or resistant subgroups. Our preliminary analysis suggests that the most effective agent, possibly methotrexate, should be used first if the objective is to get as many patients into remission as quickly as possible.

Sealant use in public and private insurance programs

Dental sealants are a safe and efficacious method for preventing caries in pits and fissures. An increase in sealant use has been observed in the NHANES III survey. However this increase still accounts for less than one fifth of children aged 5-17 having sealants on their teeth. Reimbursement and coverage of sealants by public and private insurance programs have lagged behind the widespread acceptance of this methodology by the profession. Medicaid preventive services are poorly used by patients and the profession: and the inclusion of sealants in traditional, indemnity, fee-for-service commercial plans has been inconsistent. Managed care programs include dental sealants, but lack financial incentives to increase their use.

Genome scan of human systemic lupus erythematosus: evidence for linkage on chromosome 1q in African-American pedigrees

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by production of autoantibodies against intracellular antigens including DNA, ribosomal P, Ro (SS-A), La (SS-B), and the spliceosome. Etiology is suspected to involve genetic and environmental factors. Evidence of genetic involvement includes: associations with HLA-DR3, HLA-DR2, Fcgamma receptors (FcgammaR) IIA and IIIA, and hereditary complement component deficiencies, as well as familial aggregation, monozygotic twin concordance >20%, lambdas > 10, purported linkage at 1q41-42, and inbred mouse strains that consistently develop lupus. We have completed a genome scan in 94 extended multiplex pedigrees by using model-based linkage analysis. Potential [log10 of the odds for linkage (lod) > 2.0] SLE loci have been identified at chromosomes 1q41, 1q23, and 11q14-23 in African-Americans; 14q11, 4p15, 11q25, 2q32, 19q13, 6q26-27, and 12p12-11 in European-Americans; and 1q23, 13q32, 20q13, and 1q31 in all pedigrees combined. An effect for the FcgammaRIIA candidate polymorphism) at 1q23 (lod = 3.37 in African-Americans) is syntenic with linkage in a murine model of lupus. Sib-pair and multipoint nonparametric analyses also support linkage (P < 0.05) at nine loci detected by using two-point lod score analysis (lod > 2.0). Our results are consistent with the presumed complexity of genetic susceptibility to SLE and illustrate racial origin is likely to influence the specific nature of these genetic effects.

A survey of United States rheumatologists concerning effectiveness of disease-modifying antirheumatic drugs and prednisone in the treatment of rheumatoid arthritis

OBJECTIVE

To collect the ratings of American rheumatologists regarding relative short-term and long-term effectiveness of disease-modifying antirheumatic drug (DMARD) therapy in the treatment of rheumatoid arthritis and to compare these data with results of a meta-analysis of randomized, controlled clinical trials (RCTs) of these drugs.

METHODS

A survey was mailed to 3,200 United States rheumatologists who were members of the American College of Rheumatology during the summer of 1996. The survey was completed by 645 rheumatologists.

RESULTS

Methotrexate (MTX) was rated as substantially more effective than any other DMARD after both 1 year and 4 years of therapy. At 1 year, more than 90% of rheumatologists rated MTX as "good or excellent," compared with 35% giving a similar rating to intramuscular (IM) gold, the second-ranked DMARD. At 4 years, MTX was rated as "good or excellent" by 65%, compared with 53% for combinations, 30% for prednisone, and 11% for hydroxychloroquine, the second-ranked single DMARD. These ratings reflect results of long-term observational studies, but differ considerably from a meta-analysis of results of short-term RCTs, in which the efficacy of MTX, sulfasalazine, penicillamine, and IM gold were indistinguishable.

CONCLUSION

The ratings of US rheumatologists regarding effectiveness of DMARD therapies are in agreement with observational data, but differ substantially from results of RCTs. These findings suggest that observational studies may yield useful and important information about treatment results, which are complementary to, but not available from, the RCT model. Regulatory agencies should consider long-term observational studies as a part of the evaluation of drugs.

Health services research and systemic lupus erythematosus: a reciprocal relationship

Many other statistical and epidemiologic approaches have been used in studies of systemic lupus erythematosus. Many of these, such as multivariate analysis and cost-benefit analysis, have substantially added to our understanding of the disease. However, in these instances it has been a clear application of the technique to a clinical problem. In the four areas I described, there was a convergence of clinical dilemmas and methodologic improvements, with the clinical problem actually contributing to the development of the methodologic technique used to address the question. In conclusion, major methodologic advancements in health services research and clinical epidemiology have developed pari passu with studies of the natural history of systemic lupus erythematosus. In some circumstances the clinical questions drove methodologic innovation and in other cases the methodologic studies were rapidly adopted and adapted to clinical investigation. It is unlikely that this was happenstance. We can anticipate that future investigations in lupus will utilize innovative techniques in health services research.

A preliminary evaluation of hydroxyurea for the treatment of rheumatoid arthritis

OBJECTIVE

To obtain preliminary evidence on the safety and efficacy of low dose hydroxyurea as a treatment for rheumatoid arthritis (RA).

METHODS

Five patients with active RA unresponsive to conventional therapy were entered into a 12 week, open label trial of hydroxyurea followed by a one month postdrug evaluation.

RESULTS

Three of the 4 patients completing the study had a decrease in morning stiffness and number of swollen and tender joints. All 4 patients had a decrease in pain and an increase in function as measured by a modified health assessment questionnaire. No patient had improvement in sedimentation rate, C-reactive protein, or subjective measures of global well being. However, 3 of the 4 patients had disease flare after the drug was withdrawn, demonstrated by increased number of swollen and tender joints.

CONCLUSION

Low dose hydroxyurea may be effective in the treatment of RA, but confirmation will require further testing by a randomized double blind placebo controlled trial of patients with a broader spectrum of disease severity over a longer period of therapeutic intervention.

The effect of cyclic-AMP on the regulation of c-myc expression in T lymphoma cells

Myc is implicated in the control of growth in a variety of cell types. I investigated c-myc gene expression in several lymphoid cell lines to determine the response to cyclic AMP. Cyclic AMP causes a precipitous decline in c-myc message concentration that precedes G1 cell cycle arrest in wild type S49 cells but not in KIN- cells that lack cAMP dependent PKA activity. In wild-type S49 cells washout of cyclic AMP restores c-myc message levels within 2 h but does not relieve the G1 arrest until 10 h later. Transcription runoff studies demonstrate inhibition of both transcriptional initiation and prolongation of initiated transcripts. However, the degree of inhibition is insufficient to explain the absence of detectable myc message suggesting that the predominant effect of cyclic AMP is to destabilize the c-myc message. In contrast to wild-type cells, the "Deathless" mutant S49 cell line is viable when arrested in G1 by exposure to cyclic AMP and has preserved c-myc expression. Thus, in S49 cells down regulation of c-myc expression appears to be associated with loss of viability rather than G1 cell cycle arrest. Interestingly, CEM human T lymphoma cells do not arrest in G1 phase when exposed to cyclic AMP in spite of losing detectable c-myc gene expression. This suggests that in some T lymphoma cells c-myc gene expression may not be necessary for cell cycle progression and proliferation.

The treatment of rheumatic carditis: a review and meta-analysis

We performed a meta-analysis of the literature on the treatment of established rheumatic carditis to determine if corticosteroid therapy is superior to salicylates in preventing the sequela of inflammation--valvular damage. We identified 22 reports of comparative trials published since the introduction of corticosteroids in 1949. Five of the 22 studies met the criteria we established for the meta-analysis, which included using randomization and a 1-year follow-up for the presence of a new pathologic apical systolic murmur. Based on the meta-analysis, the advantage of corticosteroid treatment over salicylates in preventing a pathologic murmur at 1 year posttreatment is not statistically significant (estimated odds ratio 0.88; 95% confidence interval: 0.53 to 1.46). However, the meta-analysis is dominated by 1 large negative trial, and there was significant heterogeneity in the results obtained from the studies in the meta-analysis; thus, the question of whether corticosteroid therapy is marginally superior to salicylates for the prevention of valvular heart disease from rheumatic fever remains open.

Opposite effects of cyclic AMP on the expression of the genes encoding ribonucleotide reductase in Swiss 3T3 and RAT 1 cells

RAT-1 and Swiss mouse 3T3 cells are fibroblast cell lines that differ in their response to agents that elevate cyclic AMP levels. We examined the effect of agents that increase cyclic AMP on the expression of the genes that encode the two subunits of ribonucleotide reductase in these two cell lines. While serum stimulation leads to comparable expression in both cell lines, agents that increase cyclic AMP result in increased gene expression in Swiss 3T3 cells but diminished expression in RAT-1 cells. In addition, forskolin could inhibit serum or insulin augmented entry into S phase in RAT-1 cells, while promoting entry in Swiss 3T3 cells. Thus, in fibroblasts differential response to cyclic AMP is evident at the level of ribonucleotide reductase gene expression.

Ribonucleotide reductase gene expression during cyclic AMP-induced cell cycle arrest in T lymphocytes

In both 3T3 mouse fibroblasts and S49 mouse T lymphocytes the genes encoding both subunits of ribonucleotide reductase are expressed beginning in late G1 phase. In studies reported here, we compared the expression of the genes that code for the M1 and M2 subunits of ribonucleotide reductase in S49 cells, which are arrested in G1 phase by agents that increase cyclic AMP, with those from CEM human T lymphoma cells that are unaffected by exposure to dibutyryl cyclic AMP. Dibutyryl cyclic AMP treatment results in a prompt steady diminution of M2 mRNA concentration to levels at or below that of elutriated G1 cell-cycle-specific populations in S49 cells, in contrast to CEM cell M2 mRNA, which is unchanged. M1 mRNA concentration decreases more slowly than M2 mRNA in S49 cells and marginally, if at all, in CEM cells. The time course of diminution of the M2 message concentration by dibutyryl cyclic AMP in S49 cells is similar to that obtained when cells are treated with actinomycin D and to the combination of the two agents. This suggests that cyclic AMP and actinomycin D may act similarly on ribonucleotide reductase gene expression. Furthermore, cycloheximide pretreatment diminishes the effect of dibutyryl cyclic AMP, indicating that the effect might be mediated by a labile protein. Transcription runoff assays suggest a diminution of transcription rate for the M2 gene in S49 cells treated with dibutyryl cyclic AMP and a transient decline in the M1 transcription rate. These data suggest that dibutyryl cyclic AMP diminishes the transcription of ribonucleotide reductase genes in sensitive cells and that this and the short half-life of the M2 message are major factors in the disappearance of the M2 messenger RNA from dibutyryl cyclic AMP-treated cells although other mechanisms may also play a role. These events clearly precede any alteration in cell cycle distribution and thus they may contribute to G1 arrest.

Synergistic and coordinate expression of the genes encoding ribonucleotide reductase subunits in Swiss 3T3 cells: effect of multiple signal-transduction pathways

Ribonucleoside-diphosphate reductase (ribonucleotide reductase, EC 1.17.4.1) is the enzyme responsible for the in vivo production of deoxyribonucleotides for DNA synthesis and is essential for cell proliferation. We examined the signal transduction pathways leading to expression of the M1 and M2 subunits of this enzyme in Swiss 3T3 mouse fibroblasts by Northern blot analysis. Stimulation of quiescent cells resulted in coordinate expression of both subunits, beginning at 8 hr after serum addition, in late G1 phase, and peaking at 18-24 hr. Serum increased M2 message to 30 to 50 times that of quiescent cells, in contrast with M1 message, which was increased 10 times. Agents that elevated cAMP, including forskolin, and the cAMP analogue 8-bromo-cAMP modestly stimulated gene expression. Each of these agents was synergistic with insulin, and these combinations induced expression equivalent to that induced by serum stimulation. Likewise, agents that activate protein kinase C such as phorbol 12,13-dibutyrate, bombesin, and vasopressin were also synergistic with insulin with respect to ribonucleotide reductase gene expression, as was epidermal growth factor, which stimulates receptor tyrosine kinase activity. The time course for induction of mRNA expression by each of these agents alone or in combination was identical to that for induction stimulated by serum. Finally, the synergistic effects apparent in Northern analysis of ribonucleotide reductase gene expression were mirrored in parallel determinations of DNA synthesis. Thus, the combinatorial nature of signal transduction pathways resulting in proliferation of Swiss 3T3 cells is expressed at the level of ribonucleotide reductase gene expression.

Deoxyadenosine- and cyclic AMP-induced cell cycle arrest and cytotoxicity

We compared deoxyadenosine (AdR)- and cyclic AMP (cAMP)-induced cell cycle arrest and cytotoxicity in wild type and mutant S49 cells to determine whether they resulted from the same or different mechanisms. Cyclic AMP and deoxyadenosine are synergistic rather than additive in cytotoxicity assays, suggesting different mechanisms of toxicity. Although cyclic AMP causes cell death after 72 h, in concentrations sufficient to result in cell cycle arrest it is reversible with virtually no cytotoxicity for at least 24 h, whereas AdR-induced cell cycle arrest is lethal and irreversible. AdR-induced G1 cell cycle arrest results in diminished ribonucleotide reductase activity but the kinetics of this inhibition differ from cyclic AMP-induced cell cycle arrest. Cyclic AMP arrest and cytotoxicity depend on cyclic AMP-dependent protein kinase (PKA) activity, whereas AdR toxicity does not differ between cell lines with or without PKA activity. Furthermore, deoxycytidine prevents AdR cell cycle arrest and cytotoxicity but has no effect on cyclic AMP G1 arrest. Finally, comparison of cytofluorographic patterns of G1-arrested cells suggests that the AdR block is later in G1 than cyclic AMP-induced cell cycle arrest. In summary, these data show that while the mechanisms of cell cycle arrest and cytotoxicity of cyclic AMP and deoxyadenosine are uncertain, they do appear to involve different pathways.

Effect of cyclic AMP on the cell cycle regulation of ribonucleotide reductase M2 subunit messenger RNA concentrations in wild-type and mutant S49 T lymphoma cells

Ribonucleotide reductase activity in S49 T lymphoma cells is cell cycle regulated by de novo protein synthesis of the M2 subunit. There is maximal enzyme activity in S and G2/M phase with low activity and low concentrations of the M2 subunit in G1 phase. Pharmacologic concentrations of cyclic AMP arrest S49 cells in the G1 phase of the cell cycle. We investigated the effect of cyclic AMP on M2 messenger RNA concentrations using RNA from exponentially growing and elutriated, cell cycle-enriched populations. To discern whether cyclic AMP-induced G1 arrest was associated with low concentrations of M2-specific messenger RNA, we probed blots with a full-length cDNA for M2. Cell cycle variation in M2 messenger RNA concentrations was similar in wild-type, hydroxyurea-resistant cells with amplified M2 activity, and cyclic AMP-dependent protein kinase-deficient cell lines. All lines had low amounts of M2-specific mRNA in early G1, an increase at the late G1/early S phase interface, a decrease in mid S phase, and another increase in late S phase that continued through G2/M. These concentrations did not directly correlate with enzyme activity, suggesting other regulatory effects might participate in determining ribonucleotide reductase activity. Cyclic AMP exposure appeared to induce cell cycle arrest in early G1 with low M2-specific messenger RNA concentration. This effect reversed upon washout of the cyclic AMP and was dependent on functional cyclic AMP-dependent protein kinase (PKA). These results suggest that cyclic AMP arrests S49 mouse T lymphoma cells in early G1 prior to transcriptional activation of the M2 gene.

M2 subunit of ribonucleotide reductase is a target of cyclic AMP-dependent protein kinase

Cyclic AMP arrests T lymphocytes in the G1 phase of the cell cycle, and prolonged exposure results in cytolysis. Both of these effects require cyclic AMP-dependent protein kinase. We recently observed that some S49 mouse T lymphoma cell lines selected for hydroxyurea resistance were not arrested in G1 by cyclic AMP. Further analysis revealed that these cell lines were cyclic AMP-dependent protein kinase deficient, and conversely, other cyclic AMP-dependent protein kinase deficient cell lines not selected for hydroxyurea resistance were two- to threefold more hydroxyurea resistant. However, hydroxyurea is a specific inhibitor of ribonucleotide reductase and does not inhibit this kinase. We subsequently showed that cyclic AMP-dependent protein kinase will phosphorylate the M2 but not the M1 subunit of ribonucleotide reductase in vitro, and this phosphorylation will diminish CDP reductase activity. In vivo phosphorylation of M2 occurred under conditions similar to those that generate cell cycle arrest. We conclude that the M2 subunit of ribonucleotide reductase can be a target of cyclic AMP-dependent protein kinase. The phosphorylated enzyme has diminished activity, and this may play a role in cyclic AMP-induced lymphocyte cell cycle arrest.

Deoxyadenosine toxicity and cell cycle arrest in hydroxyurea-resistant S49 T-lymphoma cells

Hydroxyurea-resistant S49 T-lymphoma cells have increased ribonucleotide reductase activity and deoxyribonucleoside triphosphate pools when compared with wild-type cultures. If ribonucleotide reductase inhibition is the mechanism by which deoxyadenosine is cytotoxic, then hydroxyurea (HU)-resistant S49 cells might be more resistant to deoxyadenosine toxicity when adenosine deaminase is inhibited than wild-type cells. Five S49 cell lines resistant to varying concentrations of HU were compared with wild-type cells by measuring CDP reductase activity, deoxyribonucleoside triphosphate pools, and deoxyadenosine toxicity. All five cell lines resistant to increasing concentrations of HU exhibited a twofold increase in resistance to deoxyadenosine toxicity when compared to wild type, and the resistance was proportional to the twofold increased pools of dNTPs in these cell lines but was less than the six- to eight fold increase in ribonucleotide reductase activity. In both wild-type and mutant cell lines, deoxyadenosine toxicity was accompanied by the accumulation of deoxyadenosine triphosphate and reduction of the other dNTPs; however, only dGTP greatly diminished. Exogenous addition of deoxycytidine decreased the dATP accumulation by about 20%, but also resulted in increases in the dCTP, dTTP, and dGTP pools. The S49 cells arrested in G1 phase when exposed to dAdo, although hydroxyurea-resistant cells required higher dAdo concentrations to elicit G1-phase arrest than wild-type cells. Deoxycytidine prevented dAdo-induced G1 arrest in all cell types. In summary, these data support the hypothesis that deoxyadenosine-induced dATP accumulation results in inhibition of ribonucleotide reductase and that this may be the mechanism for both cell cycle arrest and cytotoxicity in S49 T-lymphoma cells.

The diagnosis of polyarteritis nodosa. I. A literature-based decision analysis approach

We investigated diagnostic testing in polyarteritis nodosa (PAN) by calculating, from published data, the sensitivity and specificity of visceral angiography and muscle, nerve, testicle, kidney, and liver biopsy. Test sequence strategies were constructed by Bayesian inference using a computer program written for this purpose. Test sequences were compared with an aggressive strategy consisting of repeated tests until there was a positive finding or until the available tests were exhausted, and a conservative strategy consisting of 1 biopsy procedure plus angiography. The Bayesian analysis agreed most closely with the conservative approach for most prior probabilities (degree of suspicion) that a patient had PAN. The aggressive strategy had an overall sensitivity of 90% and specificity of 91%, whereas the conservative strategy was 85% sensitive and 96% specific. Furthermore, the aggressive strategy was more costly ($2,986 versus $1,961) and had a higher rate of morbidity (3.8 versus 2.7 days of hospitalization per patient evaluated) than did the conservative strategy. The mortality rates of both strategies were equivalent (approximately 0.05 deaths per hundred patients evaluated). The per-case cost of diagnosis increased as prevalence decreased, and at 10% prevalence, the aggressive strategy cost more than $17,000 per case diagnosed. Sensitivity analysis revealed that the strategies were moderately affected by the test characteristics, within reasonable assumptions, but that the differences in conservative and aggressive approaches remained. Thus, our analysis based on available data and the assumption of test independence suggests that the preferred diagnostic evaluation of patients with symptoms suggestive of PAN consists, in most cases, of a single biopsy procedure, with angiographic evaluation if necessary.

The diagnosis of polyarteritis nodosa. II. Empirical verification of a decision analysis model

We evaluated our literature-based estimates of diagnostic test characteristics and aggressive and conservative strategies for the diagnosis of polyarteritis nodosa (PAN) by reviewing 1980 through 1985 data from the University of Chicago Medical Center, Michael Reese Hospital, and Northwestern University Medical School. Test specificity was calculated by reviewing pathology and radiology reports on all relevant procedures done at the University of Chicago Medical Center in 1984 and 1985. There were no reports of false-positive findings (including angiography); thus, test specificity was 100% for muscle, nerve, kidney, liver, and testicular biopsy, which was comparable with our literature-based estimate of 97%. Test sensitivity was based on the 18 confirmed cases of PAN from the 3 institutions and was similar to that in published reports, ranging from 0% for liver biopsy to 100% for visceral angiography. Review of each case for diagnostic test sequence showed an average of 2 diagnostic procedures to confirm the diagnosis (range 1-6). Eight of 18 patients were evaluated according to the conservative strategy we proposed from our literature-based decision analysis approach. No patient was evaluated with the aggressive strategy, although 1 patient had 6 invasive procedures. Of the remaining 10 patients, 9 represented cases that might have been confirmed had the conservative approach been used, and if it had been used, 6 patients would have had the diagnosis confirmed. Thus, the minimum sensitivity of our conservative strategy is 78%, although based on these data, it could be as high as 100%.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognosis in SLE: comparison of Markov model to life table analysis

A Markov model of prognosis was evaluated by comparing the duration of disease activity states and life expectancy with Kaplan-Meier survival curves for 98 patients with systemic lupus erythematosus with 1080 patient-years of observation. A four state (remission, active, flare and death) homogeneous Markov chain was constructed to determine the transition probabilities between disease states, the probability of disease states over the subsequent 25 years, time in each disease state, and life expectancy. Approximately 85% of the clinical course of patients was in the active disease state; no patient made a transition directly between remission and flare; virtually all deaths occurred from the flare disease state. The proportion of the patient population in each disease state over time provided a convenient graphic summary of the natural history of SLE that supplemented the Kaplan-Meier survival curves. A Markov model analysis yields a clinically useful description of outcome for multistate diseases that supplements survival curves.

Deoxyribonucleotide metabolism and cyclic AMP resistance in hydroxyurea-resistant S49 T-lymphoma cells

We investigated the cell cycle regulation of deoxyribonucleoside triphosphate (dNTP) metabolism in hydroxyurea-resistant (HYUR) murine S49 T-lymphoma cell lines. Cell lines 10- to 40-fold more hydroxyurea-resistant were selected in a stepwise manner. These HYUR cells exhibited increased CDP reductase activity (5- to 8-fold) and increased dNTP pools (up to 5-fold) that appeared to result from increased activity of the M2 subunit (binding site of hydroxyurea) of ribonucleotide reductase. These characteristics remained stable when the cells were grown in the absence of hydroxyurea for up to 2 years. In both wild type and hydroxyurea-resistant cell populations synchronized by elutriation, dCTP and dTTP pools increased in S phase, whereas dATP and dGTP pools generally remained the same or decreased, suggesting that allosteric effector mechanisms were operating to regulate pool sizes. Additionally, CDP reductase activity measured in permeabilized cells increased in S phase in both wild type and hydroxyurea-resistant cells, suggesting a nonallosteric mechanism of increased ribonucleotide reductase activity during periods of active DNA synthesis. While wild type S49 cells could be arrested in the G1 phase of the cell cycle by dibutyryl cyclic AMP, hydroxyurea-resistant cell lines could not be arrested in the G1 phase by exogenous cyclic AMP or agents that elevate the concentration of endogenous cyclic AMP. These data suggest that cyclic AMP-generated G1 arrest in S49 cells might be mediated by the M2 subunit of ribonucleotide reductase.

Selection and characterization of mutant S49 T-lymphoma cell lines resistant to phosphonoformic acid: evidence for inhibition of ribonucleotide reductase

Phosphonoformic acid (PFA) and its congener phosphonoacetic acid (PAA) are inhibitors of viral replication whose mechanism of action appears to be the inhibition of viral DNA polymerase. These drugs inhibit mammalian DNA polymerase to a lesser extent. We sought to characterize the effects of phonoformic acid on mammalian cells by examining mutants of S49 cells (a mouse T-lymphoma line), which were selected by virtue of their resistance to phosphonoformic acid. The 11 mutant lines that were resistant to growth inhibition by 3 mM PFA had a range of growth rates, cell cycle distribution abnormalities, and resistance to the inhibitory effects of thymidine, acycloguanosine (acyclovir), aphidicolin, deoxyadenosine, and novobiocin. Most mutant lines had pools of ribonucleoside triphosphates and deoxyribonucleoside triphosphates similar to those of wild-type S49 cells. However, one line (PFA 3-9) had a greatly elevated dCTP pool. When this mutant line was further characterized, no apparent defect in DNA polymerase alpha activity was seen, but an increased ribonucleotide reductase activity, as assayed by CDP reduction in permeabilized cells, was observed. The CDP reductase activity in the PFA 3-9 cells decreased to wild-type control levels, and the CDP reductase activity of wild-type cells was also greatly reduced when PFA (2-3 mM) was added to permeabilized cells during the enzyme assay. These results demonstrate that PFA can directly inhibit ribonucleotide reductase activity in permeabilized cells. In addition, when PFA was added to exponentially growing cultures of either wild-type or PFA 3-9 mutant cells, the drug caused an arrest in S phase of the cell cycle and a decrease in all four deoxyribonucleotide pools, with the most dramatic decrease in the dCTP pools. The reduction in the dCTP pool level could be reversed by addition of exogenous deoxycytidine, but this reversed PFA toxicity only marginally. These observations suggest that PFA is an inhibitor of mammalian ribonucleotide reductase and that partial resistance to PFA can be effected by mutation to increased CDP reductase activity resulting in a large dCTP pool. This mutation results in less than twofold resistance to PFA, suggesting that other sites of inhibition coexist.

Ribonucleotide reductase activity and deoxyribonucleoside triphosphate metabolism during the cell cycle of S49 wild-type and mutant mouse T-lymphoma cells

We investigated deoxyribonucleoside triphosphate metabolism in S49 mouse T-lymphoma cells synchronized in different phases of the cell cycle. S49 wild-type cultures enriched for G1 phase cells by exposure to dibutyryl cyclic AMP (Bt2cAMP) for 24 h had lower dCTP and dTTP pools but equivalent or increased pools of dATP and dGTP when compared with exponentially growing wild-type cells. Release from Bt2cAMP arrest resulted in a maximum enrichment of S phase occurring 24 h after removal of the Bt2cAMP, and was accompanied by an increase in dCTP and dTTP levels that persisted in colcemid-treated (G2/M phase enriched) cultures. Ribonucleotide reductase activity in permeabilized cells was low in G1 arrested cells, increased in S phase enriched cultures and further increased in G2/M enriched cultures. In cell lines heterozygous for mutations in the allosteric binding sites on the M1 subunit of ribonucleotide reductase, the deoxyribonucleotide pools in S phase enriched cultures were larger than in wild-type S49 cells, suggesting that feedback inhibition of ribonucleotide reductase is an important mechanism limiting the size of deoxyribonucleoside triphosphate pools. The M1 and M2 subunits of ribonucleotide reductase from wild-type S49 cells were identified on two-dimensional polyacrylamide gels, but showed no significant change in intensity during the cell cycle. These data are consistent with allosteric inhibition of ribonucleotide reductase during the G1 phase of the cycle and release of this inhibition during S phase. They suggest that the increase in ribonucleotide reductase activity observed in permeabilized S phase-enriched cultures may not be the result of increased synthesis of either the M1 or M2 subunit of the enzyme.

The risk ratio is insufficient for clinical decisions. The case of prophylactic cholecystectomy

The medical literature contains studies that recommend both for and against prophylactic cholecystectomy when cholelithiasis is present. To investigate whether differing analytic techniques contribute to these disparate recommendations, we analyzed the decision to "wait and see" or "operate now," using both risk ratio and life expectancy analysis on the same data base. With intermediate symptom incidence estimates the risk ratio strongly favored an "operate now" approach, because it lessened the risk of death from gallbladder disease by up to 19-fold. In the group most favored by immediate surgery, 25-year-old men, risking death with immediate surgery increased life expectancy by only one percent (168 days). The risk ratio increased to over 30 for this group with the low incidence estimates, but the difference in life expectancy decreased to 120 days. With the high incidence estimates, the risk ratio declined to 16.4 and the life expectancy difference increased to 186 days. These data demonstrate that (1) the risk ratio can imply a course of action that is different from that implied by life expectancy analysis, and (2) the maximum expected return on the risk of immediate death with elective surgery for silent gallstones is only a one percent increase in life expectancy. This analysis suggests that single measures of effect such as the risk ratio and life expectancy do not capture all the information necessary to make an informed decision.

DNA synthesis inhibitors block protein synthesis in the human lymphocyte

We examined the requirement for early DNA synthetic events in the protein synthetic response of PHA-stimulated human lymphocytes using specific DNA synthesis inhibitors. The incorporation of H3-thymidine into DNA and H3-leucine into protein was assessed in PHA-stimulated lymphocytes cultured with cytosine arabinoside (8.5 X 10(-6)M), hydroxyurea (1.0 X 10(-2)M) or mitomycin-C (1.5 X 10(-2)M), each of which reduced DNA synthesis to the level of unstimulated lymphocytes. Under those conditions, protein synthesis was suppressed to 2, 14 and 1% of uninhibited cells at 48 h, respectively. Delaying addition of these inhibitors to 6, 12 and 24 h after initiation of PHA stimulation resulted in a parallel loss of inhibition of both RNA and protein synthesis. However, during the first 24 h of uninhibited mitogen stimulation, there is no DNA synthesis as measured by either H3-thymidine uptake or by flow cytometry. In contrast to the inhibition of protein synthesis when measured after 48 h, PHA-stimulated H3-leucine incorporation during the first 24 h was not affected by DNA synthesis inhibition. These results suggest that early events related to DNA synthesis are required for optimum mitogen-induced protein and RNA synthesis, but that new DNA synthesis does not occur until after 24 h of mitogen stimulation.

A multicenter study of outcome in systemic lupus erythematosus. I. Entry variables as predictors of prognosis

A retrospective study of factors influencing survival in 1,103 patients with systemic lupus erythematosus (SLE) was carried out at 9 university centers diverse in geographic, socioeconomic, and racial characteristics. The mortality and disease characteristics of the patients at study entry varied widely among centers. The survival rates from the time patients with a diagnosis of SLE were first evaluated at the participating center was 90% at 1 year, 77% at 5 years, and 71% at 10 years. Patients with a serum creatinine greater than 3 mg/dl at study entry had the lowest survival rates: 48%, 29%, and 12% at 1, 5, and 10 years, respectively. Survival rate also correlated independently with the entry hematocrit, degree of proteinuria, number of preliminary American Rheumatism Association criteria for SLE satisfied, and source of funding of medical care. When data were corrected for socioeconomic status, race/ethnic origin did not significantly influence survival. Survival rates varied widely at different participating institutions, generally due to differences in disease severity. Place of treatment was independently associated with survival only in the second year after study entry. Disease duration before study entry did not account for the differences in disease severity.

A multicenter study of outcome in systemic lupus erythematosus. II. Causes of death

Causes of death were examined for 1,103 systemic lupus erythematosus patients who were followed from 1965 to 1978 at 9 centers that participated in the Lupus Survival Study Group. A total of 222 patients (20%) died. Lupus-related organ system involvement (mainly active nephritis) and infection were the most frequent primary causes of death. Causes of death were similar throughout the followup period. Hemodialysis had little impact on the length of survival for patients with nephritis. Active central nervous system disease and myocardial infarction were infrequent causes of death. There were no deaths from malignancy.

Deciding whether the conclusions of studies are justified: a review

Critical review of original studies is a major source of medical information for the physician; it necessitates a clear understanding of the research objective of the study. The design of the study, whether experimental or observational, should be appropriate to answer the research question and, further, the study should employ accurate and precise measurements on a suitable group of subjects. The critical reader, aware of the principle of study design and analysis, can assess the validity of the author's conclusions through careful review of the article. A guide to the analysis of an original article is presented here. The reader is asked to formulate questions about a study from the abstract. The answers to these questions, which form the basis for acceptance or rejection of the author's conclusions, are in general available in the body of an article. This technique is demonstrated with two fictional studies about patients with angina.

The rheumatic manifestations of leprosy (Hansen disease)

Leprosy is a rare disorder in the United States, yet the rheumatic features of the disease appear to be common and frequently are the primary complaint. We observed rheumatic syndromes of erythema nodosum leprosum (ENL) occurring with and without arthritis, a swollen hands syndrome, cutaneous vasculitis, or myositis in the majority (15 of 21) of our patients. These syndromes were distinctive, sometimes dramatic, and appeared to "mimic" idiopathic rheumatic diseases, substantially delaying an accurate diagnosis of leprosy in some patients. These complications were the major cause of morbidity in our 21 patients and became dominant clinical problems requiring additional chemotherapy.

Does corticosteroid therapy affect the survival of patients with systemic lupus erythematosus?

The hypothesis that corticosteroid therapy is responsible for the striking improvement in survival of patients with systemic lupus erythematosus (SLE) was investigated with two approaches: Of 250 published papers on SLE, 52 were chosen for the first analysis because they included sufficient information on diagnostic criteria and survival but were not limited to patients selected for a particular target organ. From each article percent survival by series, average duration to death, and 1 and 5 year survival curves were abstracted. Each statistic showed linear improvement in survival since the 1930s without a significant change (P greater than 0.10) in slope for the time period following the introduction of corticosteroids. The second analysis examined the effect of corticosteroid therapy on 142 patients with SLE followed at the Massachusetts General Hospital between 1922 and 1966. Although the steroid use was conservative, the patients' survival, from year of entry, was comparable to the 52 abstracted series. A prognostic index was used to stratify patients admitted in the steroid era (after 1950) for life table analysis of survival with and without steroids. Steroids had no discernible effect on overall survival in low and medium risk groups. Use of steroids was associated with improved survival among high rish patients (P less than 0.05).