14. SALES SERVICE REVENUE, NET AND ACCOUNTS RECEIVABLE

Sales

Revenue includes service revenue (patient diagnostic services and contract diagnostic services) and clinical research grants. The following table summarizes service revenue, net of contractual allowances, for the years ended December 31, 2017 and 2016:



	2017			2016
Service revenue	$	2,565		$	3,385
Less: contractual allowances and adjustments		(863	)		(1,284	)
Service revenue, net	$	1,702		$	2,101

The following summarizes by payer type for the years ended December 31, 2017 and 2016:



	2017		2016
Medicaid	$	39	$	25
Medicare		569		688
Self-pay		103		253
Third party payers		500		1,135
Contract diagnostic services		491		—
	$	1,702	$	2,101

Revenue from the Medicare and Medicaid programs account for a portion of the Company’s patient diagnostic service revenue. Laws and regulations governing those programs are extremely complex and subject to interpretation. As a result, there is at least a reasonable possibility that recorded estimates will change by a material amount in the near term.

Revenue from clinical research grants are federal or state grants awarded to the Company to fund salaries, fringe benefits, and the purchase of supplies and equipment for specific research and development projects. Clinical research grant revenue of $0.3 million in 2017 includes grants from the National Cancer Institute of the National Institutes of Health and from the State of Nebraska Department of Economic Development. The project activities involved development of ICE COLD-PCR to interrogate multiple genes taken from blood samples. The grant period ended December 31, 2017.

The Company recognized revenue from three and two customers in 2017 and 2016, respectively, that represented in the aggregate 50 percent (ranging from 15 to 20 percent) and 33 percent (ranging from 15 to 18 percent) of net revenues, respectively. No other customers represented 10% or greater of net revenue.

Accounts Receivable

The Company has provided an allowance for potential credit losses, which has been determined based on management’s industry experience. The Company grants credit without collateral to its patients, most of who are insured under third party payer agreements.

The following summarizes the mix of receivables for the years ended December 31, 2017 and 2016:



	2017			2016
Medicaid	$	37		$	22
Medicare		256			232
Self-pay		53			63
Third party payers		1,066			881
Contract diagnostic services		445			—
Other		—			—
	$	1,857			1,198
Less allowance for doubtful accounts		(1,127	)		(810	)
Accounts receivable, net	$	730		$	388