Scientists say blood test can predict treatment effectiveness in ITP
2 factors key in determing if thrombopoietin receptor agonists will work
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The size of platelets, the cell fragments that help blood clot, and the levels of certain immune cells in the body may help predict the effectiveness of thrombopoietin receptor agonists — a treatment used when other therapies fail or are unsuitable — in people with immune thrombocytopenia (ITP) who are on a maintenance dose.
Those are the findings of a new study by researchers in China who sought to identify factors that could help in prognosticating whether second-line treatment with thrombopoietin receptor agonists will be effective for certain ITP patients.
Specifically, the scientists found that taking into account mean platelet volume, or MPV, an indicator of platelet size, enabled the prediction of treatment responses in such patients. Also useful as a predictor, according to the researchers, was a patient’s neutrophil-to-lymphocyte ratio, or NLR, a marker of inflammation. Both factors can be assessed using a common laboratory test known as a complete blood test, or CBC — one used in standard clinical practice.
“As both MPV and NLR are common parameters in CBC tests and are easily available clinically, they hold promising values as prognostic indicators for [thrombopoietin receptor agonists] administration,” the researchers wrote.
Simply put, these two factors may help clinicians predict whether treatment with thrombopoietin receptor agonists is likely to help in individuals with ITP.
The study, “Platelet volume could predict the efficacy of thrombopoietin receptor agonists in the treatment of patients with primary immune thrombocytopenia,” was published in the journal Clinical and Translational Discovery.
ITP is an autoimmune disorder marked by a loss of platelets, which can lead to several forms of internal or external bleeding.
Steroids typically used as first-line treatment for ITP
First-line treatments — typically including corticosteroids, which are effective but can have serious side effects — aim to prevent platelets from being destroyed. However, when a patient’s response to initial therapies is insufficient or they’re not well tolerated, second-line treatments such as thrombopoietin receptor agonists are used to boost platelet production.
Thrombopoietin receptor agonists are medications that stimulate bone marrow — tissue inside the body’s bones where blood cells are produced — to make more platelets.
In this study, researchers from Fudan University in Shanghai assessed whether MPV and NLR could help predict a patient’s response to thrombopoietin receptor agonists in individuals with ITP.
Their work involved 27 people with chronic ITP and 15 people with chemotherapy-induced thrombocytopenia, or low platelet counts. Also enrolled in the study were 27 healthy people, who served as controls. Most of the participants were women, with a median age between 54 and 63.
Several thrombopoietin receptor agonists were assessed: 15 patients were being treated with eltrombopag (sold as Alvaiz and Promacta), eight with herombopag (approved in China under the brand name Hengqu), three with Doptelet (avatrombopag), and one with Nplate (romiplostim).
2 factors may be ‘predictive marker’ for maintenance treatment
Before treatment, platelet counts were significantly lower and NLR levels were higher in participants with ITP compared with the healthy controls. Additionally, MPV was significantly higher in the ITP patients than in the individuals with chemotherapy-induced thrombocytopenia or the controls.
After treatment, platelet counts increased and MPV decreased significantly in ITP patients who responded to thrombopoietin receptor agonists. NLR, in contrast, did not change with treatment.
However, platelet counts, MPV and NLR before treatment, or combination therapy with prednisone (a corticosteroid) could not predict the time to achieve the highest platelet levels, according to the researchers.
The ITP patients were followed for a median of 18 weeks, or about four months, in a total of 78 follow-up interviews. All achieved platelet counts higher than 30 billion/L. In 10 interviews, the thrombopoietin receptor agonist dose was reduced and in 68 it was maintained.
After reducing the dose, a reduction in platelet counts by less than 20% or an increase (in both cases relative to study start) were seen in four follow-ups. Six others, meanwhile, showed a decrease of more than 20%. There were no differences in platelet counts, MPV, and NLR between these two groups, the researchers noted.
When the treatment dose was maintained, platelet reduction of less than 20% or an increase in these cell fragments were seen in 47 follow-ups; 21 showed a decrease of more than 20%. Platelet levels, MPV, and NLR were all significantly lower when platelet counts were reduced by less than 20% or increased.
An additional analysis found that the NLR to MPV ratio in patients who maintained their therapy dose was able to predict subsequent treatment effects on platelet counts. When the ratio is lower than 0.2996, maintenance treatment may remain effective, but when it is higher, dose adjustment may be necessary to maintain platelet counts, according to the scientists.
The researchers noted that higher MPV could reflect more platelets being made to compensate for their destruction in ITP patients, while NLR could reflect the patients’ immune cell changes.
“NLR/MPV might be a predictive marker in [thrombopoietin receptor agonists] maintenance treatment,” the researchers wrote. “However, large-scale clinical trial is still warranted to validate their [MPV and NLR] clinical applications.”
