at our laboratory, the relevant information about the test is entered into our computer system, and the test sample is routed into the appropriate workflow. This number is a subset of the number of tests that we process, which includes tests distributed through our Constellation licensees. The number of tests that we process is a key metric as it tracks overall volume growth, particularly as our laboratory partners may transition from sending samples to our laboratory to our cloud-based distribution model, as a result of which our tests accessioned would decrease but our tests processed would remain unchanged.
During the six months ended June 30, 2022, we processed approximately 989,200 tests, comprised of approximately 957,200 tests accessioned in our laboratory, compared to approximately 723,900 tests processed, comprised of approximately 694,900 tests accessioned in our laboratory, during the six months ended June 30, 2021. This increase in volume primarily represents continued commercial growth of Panorama and HCS, both as tests performed in our laboratory as well as through our Constellation software platform.
The percent of our revenues attributable to our U.S. direct sales force for the six months ended June 30, 2022 was 89%, a slight decrease compared to 90% for the six months ended June 30, 2021. The percent of our revenues attributable to U.S. laboratory distribution partners for the six months ended June 30, 2022 was 7%, an increase from 5% in the same period in the prior year. Our ability to increase our revenues and gross profit will depend on our ability to further penetrate the U.S. market with our direct sales force. The percent of our revenues attributable to international laboratory distribution partners and other international sales for the six months ended June 30, 2022 was 3%, down from 5% for the six months ended June 30, 2021, due primarily to the increase in US direct sales as a percentage of revenue.
For the six months ended June 30, 2022, total revenues were $392.3 million, compared to $294.3 million in the six months ended June 30, 2021. Revenues generated from testing accounted for $384.6 million, 98% of total revenues for the six months ended June 30, 2022, compared to $260.0 million representing 88% of total revenues for the six months ended June 30, 2021. For the six months ended June 30, 2022 and 2021, no customers exceeded 10% of the total revenues on an individual basis. Revenues from customers outside the United States were $13.2 million, representing approximately 3% of total revenues for the six months ended June 30, 2022. For the six months ended June 30, 2021, revenues from customers outside the United States were $14.6 million, representing approximately 5% total revenues. Most of our revenues have been denominated in U.S. dollars, though we generate some revenue in foreign currency, primarily denominated in Euros and Singapore Dollars.
Our net loss for the six months ended June 30, 2022 and 2021 were $283.7 million and $179.9 million, respectively. This included non-cash stock compensation expense of $76.1 million and $58.3 million for the six months ended June 30, 2022 and 2021, respectively. As of June 30, 2022, we had an accumulated deficit of $1.7 billion.
COVID-19 Impact
The COVID-19 pandemic has continued to present a global public health and economic challenge that has affected our business operations and the U.S. and other major economies and financial markets. We have modified our business practices in response to the spread of COVID-19 (including temporary closures of our offices, implementing remote work policies and practices, vaccination requirements, travel restrictions, and other measures as we have deemed necessary or appropriate from time to time), and incur additional operating costs, and we may take further actions from time to time as may be required by government authorities or that we determine are in the best interests of our employees, customers and business partners. Such actions could also impact our ability to fully integrate businesses we may acquire in the future. There is no certainty that such actions will be sufficient to mitigate the continuing risks posed by the virus or otherwise be satisfactory to government authorities. If significant portions of our workforce, and particularly our laboratory staff, are unable to work effectively, including due to illness, quarantines, social distancing, recruiting and retention difficulties, government actions, including the prospect of rising interest rates, inflationary pressure, and stock market volatility, or other restrictions in connection with the COVID-19 pandemic, our operations and financial results will be impacted.
The extent to which the COVID-19 pandemic will continue to impact our business, results of operations and financial condition will depend on future developments, which continue to remain highly uncertain and cannot be predicted, including, but not limited to, the continued duration and spread of the pandemic, including the contagiousness