David Miller
Analyst · Craig-Hallum
Thanks, Ronnie. Our full results on Form 10-K will be filed with the SEC on or before July 29. Overall, we had another year of significant financial progress and success. We continue to grow our revenue in our core research service business, and we're anticipating contribution from newly launched platforms such as Lumin going forward. We currently have more than 75 unique users, and we're looking for that number to grow in fiscal year 2022.
Our full year revenue for 2021 was a record $41 million compared to $32 million for 2020, representing year-over-year growth of 28%. Income from operations was $338,000 compared to a loss of $1.9 million in the year ago period. Excluding stock comp and depreciation, we recognized income from operations of $2.1 million compared to a loss of $100,000 a year ago.
Turning the focus to the fourth quarter. Revenue increased to approximately $10.6 million compared to $8.8 million in the year ago period, an increase of $1.8 million or 21%. As discussed on our prior earnings call, fourth quarter revenue will be impacted by studies completing earlier than projected and the associated revenue was recognized in the third quarter, leading to the slight decline in quarterly sequential revenue.
We recognized a loss of $456,000 for the quarter compared to a loss of $2 million in the year ago period. Excluding stock-based comp and depreciation, we recognized a small fourth quarter gain of $7,000 compared to a loss of $1.2 million in the year ago period.
Turning to expenses, excluding stock comp and depreciation. Our cost of sales was $5.6 million for the fourth quarter of fiscal 2021 versus $5 million for the same period last year, an increase of $621,000 or 12%. The increase was primarily due to 2 factors: the first was an increase of approximately $400,000 in costs related to clinical flow studies, with a portion of this expense recognized in advance of any revenue; the second was an increase in our rent expense as we expanded our lab space during the quarter. This move should provide the additional capacity to match our expected growth. It will result, however, in additional rent expense of approximately $250,000 per quarter. As a result of these factors, there was added pressure on our gross margin for the quarter, which finished at 47% compared to 43% in the year ago period.
As we move forward, we expect improving margins for a few reasons. First, as these flow studies complete, the revenues will be recognized with some of the costs already recorded. Additionally, we will leverage our new fixed rent costs against increasing top line revenue.
Sales and marketing expense was $1.4 million compared to $1 million in the year ago period. For the year, sales and marketing expense was $5.3 million compared to $4 million in the year ago period. The increase was mainly due to compensation expenses resulting from commissions earned and salary expense as we continue the expansion of our business development team, including the creation of a dedicated Lumin sales group. Looking ahead to this year, we anticipate a continued expansion of the business development team and marketing efforts.
R&D expense for the quarter was approximately $2.1 million compared to $1.8 million in the year ago period, an increase of $250,000 or 14%. As Ronnie outlined, we've embarked on a path to increase our R&D spend to invest in transformative opportunities for the company. That spend has begun, and we anticipate quarterly R&D expenses to be in the $2 million rate for fiscal year 2022. For the year, R&D expense was $7.2 million compared to $5.8 million last year, an increase of $1.4 million or 23%.
Our G&A expense was $1.5 million compared to $2.2 million in the year ago period. The decrease was mainly due to the onetime payment in Q4 2020 to our CEO for salary not taken in prior years. Excluding the onetime catch-up payment, G&A remained flat from the prior year fourth quarter. For the full year, excluding the aforementioned payments, G&A expense increased $300,000 or 10%. While G&A will nominally increase due to the overall company growth, it should continue to decline as a percentage of revenue over the year.
Now turning to cash. We ended the year with $4.7 million in cash on the balance sheet. For the quarter, cash used in operations was $2 million, mainly due to the normal variability in the timing and accounts receivable and an increase in prepaid expenses. Cash used in investing activities was $800,000, primarily associated with CapEx investment for our slow and fast business line. With our anticipated revenue growth, we expect to be cash flow positive in fiscal year 2022.
We ended our year in a strong cash position with the ability to continue to invest in both our target discovery and our Lumin SaaS platform outlined by Ronnie.
In summation, looking back at our fiscal year 2021 results, we reached another annual revenue record as we exceeded $41 million and grew our top line by 28%. For the full year, we achieved profitability, and we are positioned to capitalize on the exciting opportunities that lie ahead.
For fiscal year 2022, we're projecting revenue growth between 10% and 20%. As we're nearing the end of our first quarter 2022, we'll provide another update in about 6 weeks when we report our first quarter results.
We will now open the call to questions.