London, Jun 1 (IANS): Researchers have developed a new method to measure levels of the anti-malarial drug hydroxychloroquine (HCQ) in patients with the rheumatic disease systemic lupus erythematosus (SLE).

According to the study, published in the journal Arthritis Research and Therapy, the analysis method may also be useful in the treatment of COVID-19.

A disadvantage of hydroxychloroquine is its side effects which can be avoided, however, if the dosage is adjusted for each patient, said the study researchers from Uppsala University in Sweden.

To achieve the protective effect against flares in SLE while also minimising the risk of side effects, the research team developed a method that can be used in the medical care system to measure hydroxychloroquine levels in the blood of SLE patients.

The method is based on high-resolution mass spectrometry and has been used at Uppsala University Hospital since December 2019.

For the results, first, the researchers went through available data on hydroxychloroquine measurements. They saw that results from measurements on whole blood, plasma and serum were not comparable with each other.

"It was shown that there were major differences between different reports, and there seemed to be very large individual differences," said study researcher Kim Kultima, Associate Professor at Uppsala University.

For this reason, the research team conducted a study together with the research team in rheumatology that compared the levels of hydroxychloroquine in plasma, serum and whole blood in SLE patients.

They concluded that the levels in whole blood were about twice as high as in serum and plasma. Whole blood analyses were also the most dependable.

"One striking result, and very important insight, was that levels in whole blood for patients prescribed the same dosage could differ by up to 15 times between individuals," Kultima said.

This indicates a large individual variation in how the medication is metabolised.

"We also have to be very careful about drawing hasty conclusions about whether hydroxychloroquine is effective with COVID-19," the study authors wrote.

What we know today is that the analysis method will hopefully lead to better data for providing the right dosages to SLE patients who are prescribed the medication," they added.

Meanwhile, Medial journal The Lancet issued a correction on a large observational study that linked the use of HCQ with increased death risk in Covid-19 patients, after more than 100 scientists and medical professionals raised questions about the integrity of data analysed in the study.