Should we test TPMT enzyme levels before starting azathioprine?

Adaptive Immunosuppression in Lung Transplant Recipients Applying Complementary Biomarkers: The Zurich Protocol

Achieving adequate immunosuppression for lung transplant recipients in the first year after lung transplantation is a key challenge. Prophylaxis of allograft rejection must be balanced with the adverse events associated with immunosuppressive drugs, for example infection, renal failure, and diabetes. A triple immunosuppressive combination is standard, including a steroid, a calcineurin inhibitor, and an antiproliferative compound beginning with the highest levels of immunosuppression and a subsequent tapering of the dose, usually guided by therapeutic drug monitoring and considering clinical results, bronchoscopy sampling results, and additional biomarkers such as serum viral replication or donor-specific antibodies. Balancing the net immunosuppression level required to prevent rejection without overly increasing the risk of infection and other complications during the tapering phase is not well standardized and requires repeated assessments for dose-adjustments. In our adaptive immunosuppression approach, we additionally consider results from the white blood cell counts, in particular lymphocytes and eosinophils, as biomarkers for monitoring the level of immunosuppression and additionally use them as therapeutic targets to fine-tune the immunosuppressive strategy over time. The concept and its rationale are outlined, and areas of future research mentioned.

A single-center experience with methotrexate in the treatment of Chinese Crohn's disease patients

OBJECTIVE

Methotrexate (MTX) can be used as an alternative for patients with Crohn's disease (CD) who are intolerant of thiopurine. This retrospective study aimed to provide some clues about MTX treatment in Chinese patients with CD.

METHODS

Medical records of 27 adult patients with CD who were treated with MTX between 2012 and 2017 at Renji Hospital were reviewed. MTX was administered at 15 mg or 20 mg intramuscularly once per week. The remission and response rates and adverse reactions of MTX were recorded and analyzed.

RESULTS

Thirteen (48.1%) of the patients achieved remission for more than 12 months, whereas four (14.8%) responded clinically. Eight (29.6%) patients discontinued MTX due to adverse events. The mean age of those who maintained remission was significantly younger than that of those who did not ([35.62 ± 10.99] years vs. [45.43 ± 11.93] years, P < 0.05). The pretreatment C-reactive protein (CRP) level was higher in the group who maintained remission than that in those who did not ([17.20 ± 17.26] mg/L vs. [6.98 ± 5.66] mg/L, P < 0.05).

CONCLUSIONS

MTX is effective and relatively safe for patients at doses of 15 mg/week or 20 mg/week and may be an alternative therapy for patients who are intolerant of thiopurine. Elderly patients with CD and patients with normal pretreatment CRP level may have a reduced response to MTX.

Screening and vaccinations in patients requiring systemic immunosuppression: an update for dermatologists

Immunomodulatory agents are becoming an increasingly important tool in the dermatologist's armamentarium against autoimmune and auto-inflammatory conditions. This review addresses the guidelines for vaccination and screening studies prior to the initiation of immunomodulatory agents. Included are discussions of vaccination schedules, hepatitis vaccination and screening, tuberculosis screening, and specific screening recommendations for antimalarials, azathioprine, cyclosporine, methotrexate, mycophenolate mofetil, tumor necrosis factor-α inhibitors, and newer medications like apremilast and tofacitinib.

Expressing thiopurine S-methyltransferase activity as units per litre of whole-blood overcomes misleading high results in patients with anaemia

BACKGROUND

Thiopurine S-methyltransferase (TPMT) phenotype analysis, expressed as TPMT activity, is established as a routine pharmacogenomic test to screen patients prior to initiating thiopurine drug therapy. Conventionally measured TPMT activity is corrected for red blood cell (RBC) parameters. Here we present evidence that supports the simplification of the TPMT assay: by expressing TPMT activity in mU/L whole blood, without undertaking any haemoglobin (Hb) correction.

METHODS

Hb concentrations were compared in consecutive samples that had been received for TPMT phenotype analysis and which were stratified into samples with high (n = 111) and samples with normal (n = 50) Hb-corrected enzyme activity. TPMT activity was also measured in samples received for full blood count determination, stratified into those with low (n = 50) and normal (n = 50) Hb. A reference interval for TPMT activity in mU/L was derived from a correlation between activity expressed in conventional units and that expressed in mU/L (n = 1563), supported by comparison with associated genotype (n = 201).

RESULTS

In the high TPMT activity group, 83% of specimens had a low Hb concentration compared with 14% of specimens in the normal TPMT group. Samples with a low Hb concentration were found to have significantly higher Hb-corrected TPMT activity than samples with a normal Hb concentration: 83 versus 44 nmol 6-methyl thioguanine /g Hb/h, P < 0.0001. These results strongly suggest that misleading high Hb-corrected TPMT activity is found in anaemic patients. Based on the reference interval for enzyme activity of 70-150 mU/L, phenotype-genotype concordance compared well with the conventional approach (88% versus 89%). Furthermore, distribution of TPMT phenotypes with activity expressed in mU/L was identical: 0.5% deficient, 11% low, 86% normal and 2.5% high, to when it was expressed in conventional units.

CONCLUSION

Expressing TPMT activity in mU/L can overcome misleading high Hb-corrected TPMT results occurring in patients with anaemia, which could lead to inappropriate treatment. Removing the need to measure RBC indices further simplifies TPMT phenotyping, leading to a more robust assay, with reduced turn-around time and cost.