Of the 27 companies in the index, 14 firms' stocks were down, while 13 companies' share prices increased.
The disclosure comes less than a week after the company said that it was out of compliance with the Nasdaq's minimum shareholder equity requirement.
Nasdaq told the company that as of June 30 its shareholder equity does not meet the minimum $2.5 million required for its shares to remain listed on the exchange.
Of the 27 companies in the index, 12 firms' share prices retreated last month, 14 companies' stocks increased, and one firm's share value was flat.
The company markets two tests for skin cancer, including DecisionDx-Melanoma for identifying high-risk Stage I and II cutaneous melanoma patients.
Nasdaq told the company that its shares have failed to meet a minimum $1 per share closing price for 30 consecutive days and may face delisting action.
Other big gainers last month included Accelerate Diagnostics and Natera, and share prices of 23 of the 27 companies in the index increased month over month.
The firm, which markets a clinical immunosequencing assay for leukemia and multiple myeloma, had originally expected to sell its shares at $15 to $17 apiece.
The company, which also trades on the Australian Securities Exchange, has 45 days to submit a plan to the Nasdaq as to regaining compliance.
Overall, the share prices for 18 of the index's 27 companies fell month over month. Exact Sciences was the only firm whose share price improved in the double digits.