For Registry, EHR, and QCDR one must have a minimum of one eligible Medicare Part B Patient (regardless of how many Measures you Report) in order to utilize that Reporting Option. There should be one Medicare patient in the denominator of at least one measure (out of the required six). The Medicare patient does not have to be in the numerator. To further clarify, one will need a Medicare patient in the population that qualifies for the measure, but one do not necessarily need to report on that patient.
Example: If one report 8 measures via EHR, Registry, or QCDR -- one only need "1" eligible Medicare patient total in order to meet the minimum requirements for the 2017 MIPS Program.
The Data completeness criteria for a quality performance category is that one needs to report at least 50 percent of the MIPS eligible clinician or group's patients that meet the measure's denominator criteria, regardless of payer.