Methotrexate polyglutamate concentrations are not associated with disease control in rheumatoid arthritis patients receiving long-term methotrexate therapy.
ABSTRACT There are limited data suggesting that methotrexate polyglutamate (MTXGlu) concentrations can guide MTX dosing in patients with rheumatoid arthritis (RA). The aim of this study was to define a therapeutic range of red blood cell (RBC) MTXGlu(n) concentrations (where n refers to the number of glutamate groups), including threshold values for efficacy and adverse effects in patients receiving long-term oral MTX treatment.
A cross-sectional study of 192 patients receiving oral MTX was undertaken. Disease activity was assessed by the swollen and tender joint counts, the C-reactive protein level, and the Disease Activity Score in 28 joints (DAS28). High disease activity was defined as a DAS28 of >3.2. A standardized questionnaire regarding common MTX adverse effects was completed.
The MTX dosage was significantly higher in patients in whom the swollen joint count and DAS28 were higher. The MTXGlu(4), MTXGlu(5), MTXGlu(3-5), and MTXGlu(1-5) concentrations were significantly higher in patients with high disease activity. After correction for age, the estimated glomerular filtration rate, and the MTX dosage, the association remained significant for MTXGlu(5). RBC folate concentrations were significantly higher in the group with high disease activity. There was no association between any MTXGlu(n) concentration and adverse effects.
In contrast to other studies, the results of the present study did not show a relationship between the MTXGlu(n) concentration and reduced disease activity in patients with RA who were receiving long-term MTX therapy. However, disease activity was influenced by the RBC folate level, which may be a more important factor than MTXGlu(n) concentrations for disease control. In accordance with the findings of previous studies, we were unable to show a relationship between MTXGlu(n) concentrations and adverse effects. Prospective studies will be important to determine whether there is a role for measuring MTXGlu(n) concentrations in patients receiving long-term treatment with MTX.
- [Show abstract] [Hide abstract]
ABSTRACT: Objective: The folate antagonist methotrexate (MTX) is an anchor drug in the treatment of rheumatoid arthritis (RA), but its mechanism of action related to the impact on folate metabolism remains elusive. Here, we investigated the cellular pharmacologic impact of MTX on peripheral blood cells of MTX-naïve and MTX-treated RA patients and healthy controls. Methods: Gene expression microarray data was used to investigate the expression of 17 genes in the folate pathway by peripheral blood cells in a cohort of 10 MTX-naïve and 25 MTX-treated RA patients, and 15 healthy controls (test cohort). Multiplex real-time PCR was used to validate the results in an independent cohort consisting of 28 MTX-naïve RA patients, 151 RA patients treated with MTX and 24 healthy controls (validation cohort). Results: Multiple folate metabolism-related genes were consistently and significantly altered between the three groups in both cohorts. Concurrent with an immune-activation gene signature, we observed significant upregulation of folate metabolizing enzymes γ-glutamyl hydrolase and dihydrofolate reductase, as well as MTX/folate efflux transporters ABCC2 and ABCC5 in the MTX-naïve RA group compared to healthy controls. Strikingly, MTX treatment normalized these differential gene expression levels to those observed in healthy controls. Conclusion: These results suggest that under inflammatory conditions, basal folate metabolism in blood cells of RA patients is markedly upregulated, whereas MTX treatment restores normal folate metabolism levels. This novel gene signature provides insight into the mechanism of MTX action, hence paving the way for development of novel folate metabolism-targeted therapies. © 2013 American College of Rheumatology.Arthritis & Rheumatology 07/2013; · 7.48 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: To investigate whether baseline concentrations of one-carbon metabolism biomarkers are associated with treatment nonresponse and adverse events in rheumatoid arthritis (RA) patients receiving methotrexate (MTX). A prospective derivation cohort (n = 285) and validation cohort (n = 102) of RA patients receiving MTX were studied. Concentrations of plasma homocysteine, serum vitamin B12 , serum folate, erythrocyte vitamin B6 , and erythrocyte folate were determined at baseline and after 3 months of treatment. Nonresponse after 3 months was assessed using the Disease Activity Score in 28 joints (DAS28) and the European League Against Rheumatism (EULAR) response criteria. Adverse events at 3 months were assessed using biochemical parameters and health status questionnaires. Analyses were corrected for baseline DAS28, age, sex, MTX dose, comedications, and presence of the methylenetetrahydrofolate reductase 677TT genotype. In the derivation cohort, the mean DAS28 scores at baseline and 3 months were 4.94 and 3.12, respectively, and 78% of patients experienced adverse events. This was similar between the 2 cohorts, despite a lower MTX dose in the validation cohort. Patients with lower levels of erythrocyte folate at baseline had a higher DAS28 at 3 months in both the derivation cohort (β = -0.15, P = 0.037) and the validation cohort (β = -0.20, P = 0.048). In line with these results, lower baseline erythrocyte folate levels were linearly associated with a 3-month DAS28 of >3.2 in both cohorts (derivation cohort, P = 0.049; validation cohort, P = 0.021) and with nonresponse according to the EULAR criteria (derivation cohort, P = 0.066; validation cohort, P = 0.027). None of the other biomarkers (levels at baseline or changes over 3 months) were associated with the DAS28 or treatment nonresponse. Baseline levels of the biomarkers and changes in levels after 3 months were not associated with incidence of adverse events. A low baseline concentration of erythrocyte folate is associated with high disease activity and nonresponse at 3 months after the start of MTX treatment and could be used in prediction models for MTX outcome. None of the investigated one-carbon metabolism biomarkers were associated with incidence of adverse events at 3 months.Arthritis & Rheumatology 11/2013; 65(11):2803-13. · 7.48 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Rapid and effective suppression of inflammation is a primary goal in the treatment of rheumatic diseases. However, the therapeutic effect of most medications may be slow to manifest, in the order of weeks or months in the case of DMARDs. Monitoring of drug concentrations allows the possibility of appropriate dose adjustment or changes in medication to achieve more rapid or better outcomes. We review the evidence for drug concentration monitoring. Despite the theoretical utility for monitoring of MTX polyglutamate concentrations in red blood cells in patients with RA, studies have not shown a clear association between concentrations and either efficacy or toxicity and routine measurement is not yet recommended. Small studies associating disease control with concentrations of anti-TNF therapies and anti-drug antibodies suggest that routine monitoring may be useful in the future. However, the data are not yet sufficient for this recommendation. With the use of allopurinol in gout, there is a putative therapeutic range for the active metabolite oxypurinol; however, adjusting the allopurinol dose to achieve a target urate concentration is likely to be most effective, and measuring oxypurinol may be best suited to assessing drug adherence. Although measuring thiopurine metabolite concentrations with AZA therapy has been shown to be useful in IBD, studies in rheumatic diseases have so far failed to confirm a useful association between concentrations and disease control or drug toxicity. Whole blood concentrations of HCQ have been associated with disease control in SLE and future studies may be able to determine a therapeutic range.Rheumatology (Oxford, England) 11/2013; · 4.24 Impact Factor
ARTHRITIS & RHEUMATISM
Vol. 62, No. 2, February 2010, pp 359–368
© 2010, American College of Rheumatology
Methotrexate Polyglutamate Concentrations Are
Not Associated With Disease Control in
Rheumatoid Arthritis Patients Receiving
Long-Term Methotrexate Therapy
Lisa K. Stamp,1John L. O’Donnell,2Peter T. Chapman,2Mei Zhang,2Jill James,2
Christopher Frampton,3and Murray L. Barclay1
Objective. There are limited data suggesting that
methotrexate polyglutamate (MTXGlu) concentrations
can guide MTX dosing in patients with rheumatoid
arthritis (RA). The aim of this study was to define a
therapeutic range of red blood cell (RBC) MTXGlun
concentrations (where n refers to the number of gluta-
mate groups), including threshold values for efficacy
and adverse effects in patients receiving long-term oral
Methods. A cross-sectional study of 192 patients
receiving oral MTX was undertaken. Disease activity
was assessed by the swollen and tender joint counts, the
C-reactive protein level, and the Disease Activity Score
in 28 joints (DAS28). High disease activity was defined
as a DAS28 of >3.2. A standardized questionnaire
regarding common MTX adverse effects was completed.
Results. The MTX dosage was significantly higher
in patients in whom the swollen joint count and DAS28
were higher. The MTXGlu4, MTXGlu5, MTXGlu3–5, and
MTXGlu1–5concentrations were significantly higher in
patients with high disease activity. After correction for
age, the estimated glomerular filtration rate, and the
MTX dosage, the association remained significant for
MTXGlu5. RBC folate concentrations were significantly
higher in the group with high disease activity. There was
no association between any MTXGlunconcentration
and adverse effects.
Conclusion. In contrast to other studies, the
results of the present study did not show a relationship
between the MTXGlunconcentration and reduced dis-
ease activity in patients with RA who were receiving
long-term MTX therapy. However, disease activity was
influenced by the RBC folate level, which may be a more
important factor than MTXGlunconcentrations for
disease control. In accordance with the findings of
previous studies, we were unable to show a relationship
between MTXGlunconcentrations and adverse effects.
Prospective studies will be important to determine
whether there is a role for measuring MTXGlunconcen-
trations in patients receiving long-term treatment with
Methotrexate (MTX) is the gold standard treat-
ment against which newer disease-modifying antirheu-
matic drugs (DMARDs) are compared, because of its
established track record in rheumatoid arthritis (RA).
The dosage of MTX required by individual patients
varies greatly and is unpredictable. The decision by a
clinician to increase the dosage is dependent on the
assessment of disease activity, the accepted upper limit
of drug dosing, and adverse effects.
In patients with RA, both a trend toward a
dose-response relationship (1,2) and no association be-
tween dose and response have been reported for MTX
(3). Serum MTX concentrations have not correlated
with disease activity (4). Recent studies suggest a nega-
tive correlation between long-chain red blood cell
(RBC) MTX polyglutamate (MTXGlun) concentrations
ClinicalTrials.gov identifier: ACTRN012606000275561.
Supported by Health Research Council of New Zealand and
Arthritis New Zealand.
1Lisa K. Stamp, FRACP, PhD, Murray L. Barclay, FRACP,
MD: University of Otago, and Christchurch Hospital, Christchurch,
New Zealand;2John L. O’Donnell, FRACP, FRCPA, Peter T. Chap-
man, FRACP, MD, Mei Zhang, PhD, Jill James, BN: Christchurch
Hospital, Christchurch, New Zealand;3Christopher Frampton, PhD:
University of Otago, Christchurch, New Zealand.
Address correspondence and reprint requests to Lisa K.
Stamp, FRACP, PhD, Department of Medicine, University of Otago,
Christchurch, PO Box 4345, Christchurch 8140, New Zealand. E-mail:
Submitted for publication March 29, 2009; accepted in revised
form October 9, 2009.
(where n refers to the number of glutamate groups) and
disease activity (3,5,6). Studies have also examined
whether polymorphisms of genes encoding the enzymes
involved in MTX transport and/or the folate pathway
may help predict the response and/or adverse effects
associated with MTX. However, to date, there is no clear
consensus regarding the most important polymorphisms
(for review, see ref. 7).
Despite its widespread use, the exact mechanism
of action of MTX remains unclear. Following adminis-
tration and absorption, serum MTX concentrations fall
rapidly (8), and MTX is transported into a variety of
cells including RBCs, white blood cells, hepatocytes, and
synoviocytes via the reduced folate carrier (RFC). Intra-
cellularly, glutamate moieties are added by folylpolyglu-
tamate synthetase (FPGS), and MTX is retained as
MTXGlun. Terminal MTX glutamates are removed by
?-glutamyl hydrolase, returning MTX to its monogluta-
mate form, which is rapidly transported out of the cell by
multidrug-resistant proteins. The intracellular concen-
trations of MTXGlunare therefore related to the bal-
ance of activity between these 2 enzymes. Ingested
folates are also transported into cells by the RFC and
folate receptor and compete with MTX as a substrate for
polyglutamation by FPGS. Thus, high concentrations of
intracellular folates result in a decrease in MTX poly-
MTX has several potential adverse effects. The
more common, but less serious, adverse effects that
often limit a patient’s willingness to continue MTX
treatment include nausea and lethargy. The more seri-
ous adverse effects, which can limit the dosage or
require MTX discontinuation, include hepatotoxicity
and myelotoxicity. Because of the inability to predict the
occurrence of these adverse effects, patients are re-
quired to have regular blood tests. Two small studies in
patients with RA demonstrated no clear association be-
tween MTXGlunconcentrations and adverse effects (5,11).
The aim of this study was to determine whether a
therapeutic range of MTXGlunconcentrations could be
defined in order to guide adjustment of oral MTX
dosing, including threshold values for efficacy and ad-
PATIENTS AND METHODS
Ethics approval was obtained from the Upper South B
Regional Ethics Committee, New Zealand. Written informed
consent was obtained from each patient.
Patients and study protocol. This cross-sectional study
was undertaken in a single center in Christchurch, New
Zealand. Patients ?18 years age with RA, as defined by the
American College of Rheumatology (formerly, the American
Rheumatism Association) (12), were recruited. Patients were
required to have been receiving oral MTX for ?3 months, and
the dosage must have been stable for ?1 month prior to study
entry. A preference was given to patients receiving MTX
monotherapy. Concomitant therapy with nonsteroidal antiin-
flammatory drugs (NSAIDs) and prednisone was allowed. A
change in the MTX dosage, introduction of another DMARD,
a change in the oral prednisone dosage, and receipt of an
intraarticular steroid injection within 1 month prior to enroll-
ment were not allowed.
Clinical assessment. Patient demographic and clinical
details were collected on standardized data collection forms.
Disease activity was assessed using the swollen joint count
(SJC), the tender joint count (TJC), the modified Health
Assessment Questionnaire (M-HAQ) (13), the physician’s
global assessment of disease activity, and the patient’s assess-
ment of pain and global assessment of disease activity. To
avoid interobserver variability, the SJC and TJC were deter-
mined by a single trained observer. The physician’s assessment
of response to MTX was measured using a 100-point visual
analog scale (VAS), where 0 ? excellent response and 100 ?
poor response. The Disease Activity Score in 28 joints
(DAS28) (14) was calculated, and low disease activity was
defined as a DAS28 of ?3.2 (15). The Clinical Disease Activity
Index (CDAI) (16) and the Simplified Disease Activity Index
(SDAI) (17) were also calculated.
A standardized questionnaire related to common
MTX adverse effects in the month preceding study entry was
developed. Adverse effects were grouped into 3 categories, as
follows: 1) gastrointestinal (GI; nausea, vomiting, diarrhea,
mouth ulcers, and decreased appetite), 2) central nervous
system (CNS; fatigue, loss of concentration, headache, dizzi-
ness, blurred vision, sleep disturbance, and weepiness), and 3)
other (hair loss, cough, fever, and shortness of breath).
Laboratory measurements. Standardized laboratory
assessments included a complete blood cell count, liver func-
tion tests, and determination of the creatine level, the eryth-
rocyte sedimentation rate (ESR), the C-reactive protein
(CRP) level, and the RBC folate level. Estimated creatinine
clearance (the estimated glomerular filtration rate [eGFR])
was calculated using the Modification of Diet in Renal Disease
study equation (18).
MTXGlu terminology and measurement. MTX, the
parent drug, contains 1 glutamate moiety and is referred to as
MTXGlu1.MTXGlu1and the products of intracellular gluta-
mation (MTXGlu2, MTXGlu3, MTXGlu4, and MTXGlu5) are
collectively referred to as MTX polyglutamates (MTXGlun).
The terms MTXGlu3–5and MTXGlu1–5refer to the sum of
each measured RBC MTXGlunconcentration.
Trough MTXGlunconcentrations were measured by
high-performance liquid chromatography, as previously de-
scribed (19). Results were normalized to an RBC count of 8 ?
1012cells, so that results were comparable and not confounded
by changes in RBC counts between individuals. All samples
were analyzed in duplicate, and the mean concentration of
each RBC MTXGlunfrom each sample was used.
Statistical analysis. The relationship between the
MTX dosage and each disease activity measure was assessed
360STAMP ET AL
using Spearman’s correlation coefficient. The relationships
between MTXGlunconcentrations and disease activity mea-
sures were first quantified using correlation coefficients. Sub-
sequently, the relationships were further explored using covari-
ate analyses that included variables known to affect disease
activity (e.g., age, sex, duration of RA, and prednisone use) as
covariates. Differences between the groups with low disease
activity and high disease activity in terms of MTXGluncon-
centrations, demographic and clinical features, and treatment
measures were tested using independent t-tests, nonparametric
Mann-Whitney U tests, chi-square tests, and Fisher’s exact
tests, as appropriate.
Further covariate analyses exploring the independent
association of MTXGlunconcentrations with disease activity
were undertaken using age, eGFR, MTX dosage, and RBC
folate level as covariates. The relationships between the pres-
ence of adverse effects and MTX dosage and MTXGlun
concentrations were tested using independent t-tests. Covari-
ate analyses including other factors that might contribute to
adverse effects (use of other DMARDS or NSAIDs, duration
of MTX treatment, and RBC folate levels) were undertaken to
establish the independent association between adverse effects
and MTX dosage and MTXGlunconcentrations. The associa-
tion between MTXGlunconcentrations and other laboratory
measurements was tested using Pearson’s correlation coeffi-
cient. Two-tailed P values less than 0.05 were considered
Demographics. Two hundred patients were re-
cruited between October 2005 and February 2008. An
ESR value was not obtained in 8 patients, and these
patients were excluded, leaving 192 in the final analysis.
Of the 192 patients, 72.9% were women, and the mean
age was 60.5 years (range 18–84 years). The mean
duration of RA was 10.5 years (range 0.25–53 years).
Among the 192 patients, 25.5% had rheumatoid nod-
ules, 63% had radiographic erosions, 80.7% were rheu-
matoid factor positive, and 76.4% were anti–cyclic cit-
rullinated peptide (anti-CCP) antibody positive. The
median dosage of MTX was 15 mg/week (range 5–25),
and all but 1 patient received folic acid at a dosage of 5
mg/week, given 3–4 days after the dose of MTX. Patients
had been receiving MTX for a median of 3 years (range
0.25–19 years) prior to study entry and had been receiv-
ing MTX at the study-entry dosage for a median of 12
months (range 1–240 months). Eighty-six of the 192
patients (44.8%) were receiving NSAIDs, and 20 pa-
tients (10.4%) were receiving another DMARD (4 sul-
fasalazine [SSZ], 9 hydroxychloroquine [HCQ], 5 both
SSZ and HCQ, 1 leflunomide [LEF], and 1 both LEF
and HCQ). Fifty-nine patients (30.7%) were receiving
oral prednisone at a mean dosage of 5.2 mg/day (range
Relationship between MTX dosage, MTXGlun
concentrations, and disease activity. There was a signif-
icant association between the MTX dosage and RBC
MTXGlu3, MTXGlu4, MTXGlu5, MTXGlu1–5, and
MTXGlu3–5concentrations (P ? 0.0001 for all). How-
ever, there was no association between the MTX dosage
and the MTXGlu1or MTXGlu2concentration (20).
The MTX dosage was higher in those patients
with a higher SJC (r ? 0.19, P ? 0.006), physician’s
global assessment score (r ? 0.3, P ? 0.0001), DAS28
(r ? 0.15, P ? 0.03), physician-rated response to MTX
(r ? 0.27, P ? 0.0001), patient’s global assessment score
(r ? 0.19, P ? 0.007), CDAI (r ? 0.25, P ? 0.0005), and
SDAI (r ? 0.25, P ? 0.0005). There was no association
between the MTX dosage and the TJC, M-HAQ score,
CRP level, ESR, pain on a VAS, or fatigue on a VAS.
Thus, despite increasing dosages of MTX, disease re-
mained active in some patients.
RBC MTXGlunprofile. MTXGlu1, MTXGlu2,
and MTXGlu3were detectable in all patients, while
MTXGlu4was detectable in 178 (92.7%) of 192 patients,
and MTXGlu5was detectable in 148 (77.1%) of 192
patients. MTXGlu3was the predominant polyglutamate,
accounting for a mean of 35.8% of the total MTXGlun.
MTXGlu1accounted for 21.7%, MTXGlu2accounted
for 20.5%, MTXGlu4accounted for 14.5%, and MTX-
Glu5accounted for 7.5%.
Association between the RBC MTXGlunconcen-
tration and disease activity measures. Univariate analy-
sis revealed a significant association between MTXGlu4,
MTXGlu5, MTXGlu1–5, and MTXGlu3–5concentrations
and the SJC, the physician’s global assessment, the
physician’s assessment of response to MTX, the DAS28,
the CDAI, and the SDAI, such that higher disease
activity was associated with higher MTXGlunconcentra-
tions (Table 1). There was also a positive correlation
between the MTXGlu3concentration and the physi-
cian’s global assessment score, the DAS28, and the
SDAI (Table 1). There was a significant association
between MTXGlu1–5concentrations and the M-HAQ
score. There was no association between any other
MTXGlunconcentration and the M-HAQ, the CRP
level, or the patient’s assessment of pain and global
assessment of disease activity on a VAS (Table 1).
Several variables are known to affect disease
activity and outcome measures in RA, including age, sex,
duration of RA, smoking, anti-CCP antibody status,
concomitant treatment with corticosteroids, NSAIDs, or
other DMARDs, and folate status. After adjustment
for these variables, patients with a higher TJC, a higher
SJC, and a higher DAS28 still had significantly higher
MTX POLYGLUTAMATES IN RA361
MTXGlu5concentrations (P ? 0.05 for all). Similarly,
patients with greater fatigue and higher M-HAQ scores
had significantly higher MTXGlu2concentrations (P ?
0.05). Taken together, these data suggest that physicians
may increase the MTX dosage in the setting of ongoing
disease activity in an effort to improve the drug effect, as
would be expected. Patients receiving a higher dosage of
MTX and having higher disease activity may therefore
be nonresponders to MTX.
RBC MTXGlunconcentrations in the group with
high disease activity and the group with low disease
activity. One hundred fourteen patients (59%) were
defined as having low disease activity (DAS28 ?3.2),
and 78 (41%) were categorized as having high disease
activity. Other than longer disease duration in the group
with high disease activity, there were no significant
differences in demographic and treatment variables be-
tween these 2 groups (Table 2).
The MTXGlu4, MTXGlu5, MTXGlu3–5, and
MTXGlu1–5concentrations were higher in the group
with high disease activity compared with the group with
low disease activity (Figure 1). In this cohort, we previ-
ously showed that age, the eGFR, and the MTX dosage
account for most variation in MTXGlunconcentrations
(20). After correction for these variables, there was no
significant difference between the group with high dis-
Univariate analysis of RBC MTXGlunconcentrations and disease activity variables*
VAS FatigueCDAI SDAI
* Values are Spearman’s correlation coefficients. The visual analog scale (VAS) was based on a 0–100 scale. RBC ? red blood cell; MTXGlu ?
methotrexate polyglutamate; M-HAQ ? modified Health Assessment Questionnaire; CRP ? C-reactive protein; DAS28 ? Disease Activity Score
in 28 joints; VAS ? visual analog scale; CDAI ? Clinical Disease Activity Index; SDAI ? Simplified Disease Activity Index.
† P ? 0.01.
‡ P ? 0.05.
Characteristics of the patients with RA according to the level of disease activity*
Low disease activity
(n ? 114)
High disease activity
(n ? 78)P
Age, mean (range) years
No. of men/no. of women
eGFR, mean ? SEM ml/minute/1.72 m2
Rheumatoid factor positive
Anti-CCP antibody positive
Duration of RA, mean (range) years
Duration of RA ?20 years
Any other DMARD
Dosage, mean (range) mg/day
MTX dosage, median (IQR) mg/week
No. of months receiving dosage, median (IQR)
76.9 ? 1.4
75.7 ? 1.9
* Except where indicated otherwise, values are the number (%). Low disease activity was defined as a
28-joint Disease Activity Score (DAS28) of ?3.2; high disease activity was defined as a DAS28 of ?3.2.
RA ? rheumatoid arthritis; eGFR ? estimated glomerular filtration rate; anti-CCP ? anti–cyclic
citrullinated peptide; NSAIDs ? nonsteroidal antiinflammatory drugs; DMARD ? disease-modifying
antirheumatic drug; MTX ? methotrexate; IQR ? interquartile range.
† Only 77 of the patients were assessed.
‡ Only 113 of the patients were assessed.
362STAMP ET AL
ease activity and the group with low disease activity in
the concentration of MTXGlu1(P ? 0.76), MTXGlu2
(P ? 0.47), MTXGlu3(P ? 0.38), MTXGlu4(P ? 0.08),
MTXGlu1–5(P ? 0.11), or MTXGlu3–5(P ? 0.08).
However, MTXGlu5concentrations remained signifi-
cantly higher in the group with high disease activity (P ?
0.02). MTXGlu5was undetectable in 25% of the group
with low disease activity compared with 19% of the
group with high disease activity (P ? 0.31).
When patients were grouped according to broad
ranges of each MTXGlunconcentration, similar percent-
ages of patients were classified as having low disease
activity, irrespective of the MTXGlunconcentration
It has been suggested that patients in whom the
MTXGlu3–5concentration is ?60 nmoles/liter are more
likely to have a good response to MTX (3). Among our
patients with a DAS28 of ?3.2, 43% had an MTXGlu3–5
concentration of ?60 nmoles/8 ? 1012RBCs, and 57%
had an MTXGlu3–5concentration of ?60 nmoles/8 ?
Figure 1. Methotrexate polyglutamate (MTXGlu) concentrations in patients with low disease activity (Disease Activity Score in 28 joints [DAS28]
?3.2) and patients with high disease activity (DAS28 ?3.2). Each dot represents an individual patient. Bars show the mean. RBC ? red blood cell.
Figure 2. Percentage of patients with low disease activity (Disease Activity Score in 28 joints [DAS28] ?3.2) according to ranges of each
methotrexate polyglutamate (MTXGlu) concentration. RBC ? red blood cell.
MTX POLYGLUTAMATES IN RA363