Mr. Reuvers added, “Looking ahead, while not perfectly linear, we expect evidence of recovery from the pandemic to begin to materialize in Q2, with progressive improvements in the second half of the year. Under these assumptions, we are reaffirming our financial outlook for 2021 based on our continued confidence in the ability to return to year-over-year revenue growth approaching 20% in the second half of 2021. Longer-term, we look forward returning to our multi-year track record of delivering annual growth of 20% or more, as we continue to develop the market for lymphedema and related chronic conditions and bring relief to patients in need.”
First Quarter 2021 Financial Results
Total revenue in the first quarter of 2021 decreased $0.9 million, or 2%, to $42.8 million, compared to $43.7 million in the first quarter of 2020. First quarter revenue continued to be negatively impacted by COVID-19, primarily from social distancing requirements and patient cancellations. These headwinds were partially offset by the continued expansion of our commercial team, effective virtual educational events and an increase in the number of Medicare patients served.
Gross profit in the first quarter of 2021 decreased $0.8 million, or 3%, to $30.2 million, compared to $31.1 million in the first quarter of 2020. Gross margin was 70.7% of revenue, compared to 71.1% of revenue in the first quarter of 2020.
Operating expenses in the first quarter of 2021 decreased $1.2 million, or 3%, to $34.3 million, compared to $35.5 million in the first quarter of 2020. The reduction in operating expenses was driven by a decrease in sales and marketing expense of $4.2 million, or 18%, to $18.8 million, primarily due to virtual sales meetings, along with lower patient training costs and reduced travel and entertainment expenses. In addition, research and development expense decreased $0.4 million, or 25%, to $1.3 million, primarily due to slower clinical studies activity as a result of COVID-19. The decrease in these expenses was offset partially by reimbursement, general and administrative expenses, which increased $3.4 million, or 31%, to $14.3 million, compared to $10.9 million in the first quarter of 2020. The increase in reimbursement, general and administrative expenses was driven by increased occupancy costs, depreciation expense, legal and professional fees, as well as personnel-related expenses due to increased headcount.
Operating loss in the first quarter of 2021 decreased $0.4 million, or 8%, to $4.1 million, compared to an operating loss of $4.5 million in the first quarter of 2020.
Income tax benefit in the first quarter of 2021 was $1.8 million, compared to $2.9 million in the first quarter of 2020. The year-over-year decrease in income tax benefit was primarily due to the net operating loss carryback claim refund recognized in the first quarter of 2020, which did not impact the tax benefit in the first quarter of 2021.
Net loss in the first quarter of 2021 was $2.3 million, or $0.12 per diluted share, compared to a net loss of $1.3 million, or $0.07 per diluted share, in the first quarter of 2020. Weighted average shares used to compute diluted net income per share were 19.5 million and 19.2 million in the first quarters of 2021 and 2020, respectively.
Adjusted EBITDA loss was $7,000 in the first quarter of 2021, compared to Adjusted EBITDA loss of $0.5 million in the first quarter of 2020.