The company said that diagnostic testing volumes, product and royalty revenues, and clinical services revenues all fell year over year.
The index's 13 percent gain was below the 39 percent surge of 2017 but occurred despite the poor performance of index stocks in December.
The firm said clinical services revenues fell during the quarter due to reduced insurance reimbursement payments and mix of testing in the prior year.
After six straight months of gains, the index saw a sharp drop in October that even positive earnings news could not stave off.
The firm said the decline in Q4 revenues was due to an account loss as well as lower insurance reimbursement and shifts away from high-value genetic testing.
Natera led the Index for the second month in a row after it announced that it intended to raise $75 million in a public stock offering.
Natera led the Index with a 61 percent increase in stock price, driven by the firm's announcement that it was entering the transplantation market.
The firm said that the decline was due to a customer shifting to internalizing genetic ordering, adverse weather, and the loss of an undisclosed commercial payor.
The decline matched the struggles of the broader stock market, though bright spots could be found with GenMark, Quidel, and NanoString all having good months.
Bloomberg reports that the DNA-for-cash deal reported in Kentucky might be a more widespread scam.
St. Jude Children's Research Hospital scientists have treated infants with X-linked severe combined immunodeficiency using gene therapy in an early phase study.
St. Louis Public Radio reports that some African Americans are turning to DNA ancestry testing to help guide genealogical searches.
In Nature this week: a genomic analysis of the snailfish Pseudoliparis swirei, ancient DNA analysis gives insight into the introduction of farming to England, and more.