Most adults with lupus or inflammatory arthritis are not at greater risk of hospitalization from COVID-19, a pair of studies said Tuesday, in what researchers said was reassuring news.

Both lupus and more common forms of arthritis cause people's immune systems to mistakenly attack their own tissues, leading to inflammation in the joints, skin, kidney, and other parts of the body.

The majority of those affected by these diseases are women.

The new studies were published in the journal Arthritis & Rheumatology and led by researchers at New York University's Grossman School of Medicine.

There was a note of concern -- the research found that patients with arthritis who took steroid medications rather than more targeted medicines known as biologic drugs were at increased risk of needing hospital care.

But the team said the findings were overall positive news for patients of these conditions, who report feeling added anxiety that their treatments make them more susceptible to COVID-19.

In the first study, researchers closely monitored the health of 226 adults, mostly black, Hispanic, and female, undergoing treatment for mild to severe forms of lupus. 

The group was surveyed or had their medical records checked between April 14 and June 1, when New York had its peak case load.

Twenty-four were hospitalized out of 83 who had confirmed or probably COVID-19 cases, and four died.

Researchers found lupus patients taking immune-suppressing drugs like mycophenolate mofetil (CellCept) and azathioprine (Imuran) had no greater risk of hospitalization than those not on them.

In the second study, researchers monitored 103 mostly white women treated between March 3 and May 4 for inflammatory arthritis (rheumatoid, psoriatic and spondyloarthritis).

Unlike osteoarthritis, these do not primarily result from joint wear and tear.

All either tested positive for COVID-19 or were probable cases. 

Twenty-seven (26 percent) were hospitalized, with four deaths (four percent).

This was comparable to the rate seen for all New Yorkers of 25 percent.

Dr Ruth Fernandez-Ruiz, who co-authored one of the papers, told AFP that when researchers began their work they were worried that the treatments the patients took, as well as organ damage caused by their conditions, would make outcomes worse. 

"People with lupus or inflammatory arthritis have the same risk factors for getting seriously ill from COVID-19 as people without these disorders," she said. 

- Steroid caution -

Arthritis patients who were taking biologic drugs such as adalimumab (Humira) and etanercept (Enbrel), weren't at higher or lower risk of hospitalization.

The same applied to hydroxychloroquine, another well established treatment for immune disorders.

Hydroxychloroquine is separately being studied as a coronavirus treatment and so the fact it neither increased nor reduced risk for COVID-19 hospitalization is more proof it doesn't work for this purpose.

Worryingly, arthritis patients taking glucocorticoids, a type of steroid, even in mild doses, were upwards of 10 times more likely to be hospitalized than those not on the drug.

Steroids work by suppressing the broader immune system, while biologics are more selective, targeting specific proteins associated with inflammation.

It is not possible to switch over all patients using steroids to other drugs.

The researchers cautioned however that the study's small sample size may be overestimating the risk.