Long-term Lab Monitoring in RA is Inefficient Save

Annals of Internal Medicine has published a retrospective study of long-term routine laboratory toxicity monitoring (lt-RLTM) in patients receiving disease-modifying antirheumatic drug (DMARD) therapy showing that most very abnormal laboratory finding occur early in therapy (first 6 months) or are anticipated or only after dose escalation.

 

This retrospective cohort study from the Netherlands looks at the lab results of 4774 patients on DMARDs, specifically noted abnormal and very abnormal test results. The "very abnormal" rante for ALT alanine aminotransferase was >300 U/L, estimated glomerular filtration rate <45 mL/min/1.73 m², hemoglobin <6 mmol/L, leukocyte count <2.0 × 10⁹/L, and platelet count <100 × 10⁹/L. 

 

A total of 4774 patients recorded 59 555 test sets over 18 383 patient-years. The probabilities of very abnormal laboratory results for the 5 tests varied from 0.2% (leukocyte count) to 6.6% (eGFR) at 2 years and from 0.3% (leukocyte count) to 11% (eGFR) at 5 years. 

 

New very abnormal results (n = 449) mostly occurred after a dose increase (6.5%), were often already known or suspected (48%), were considered to be unrelated to DMARD use (24%), or did not lead to action (36%). 

 

The incidence of less serious abnormal results was higher, as high as 39% for eGFR less than 60 mL/min/1.73 m² and 61% for Hb level below 7.5 mmol/L for females or below 8 mmol/L for males.

 

Routine laboratory monitoring after 6 months of DMARD showed that most very abnormal laboratory results were very uncommon were already clinically anticipated or occurred after dose escalation. These findings suggest a one plan fits all approach to lab monitoring is inefficient in the long term and that there is a need for better guidelines or individualized monitoring plans based on individual risk.