A quick look at Illumina (NASDAQ:ILMN) stock's performance is all you need to know how the company's first two quarters in 2017 went. Illumina's share price has soared 60% so far this year after the gene-sequencing leader beat revenue guidance in the first quarter and blew past both revenue and earnings guidance in the second quarter.

Investors will find out if Illumina's momentum will continue next week when the company announces its third-quarter earnings results. Here are three things to expect in those results.

Illumina sign and office buildings

Image source: Illumina. 

1. NovaSeq picking up steam

Illumina's latest advance in gene sequencing, the NovaSeq system, will no doubt be the most important topic of discussion related to the company's third-quarter performance. When Illumina reported its quarterly results last time around, the company said that NovaSeq orders were 30% higher than expected. There are a couple of reasons to anticipate even more momentum for NovaSeq in the third quarter.

First, Illumina's manufacturing capacity for the new system was projected to increase in the third quarter. That should help the company work down its backlog of more than 100 orders somewhat.

Second, early adopters for NovaSeq were largely commercial customers with more flexibility in their budgets. Additional demand could pick up from academic customers in the second half of the year as these organizations work through the grant application process.

However, Rebecca Chambers, Illumina's vice president of investor relations and treasury, said in August to expect only a slight sequential increase of NovaSeq placements in the third quarter. She also noted that there could be lumpiness at times with consumables revenue as customers transition to NovaSeq. It's possible that this could be seen in the third quarter.

2. Higher expenses

Even though Illumina increased its revenue growth guidance for 2017 after the terrific second-quarter results, the company didn't change its adjusted earnings per share outlook for the year. Higher revenue expectations with no corresponding higher expectations for adjusted earnings means that Illumina will be spending more money.

One reason why earnings were better than expected in the second quarter was that some expenses anticipated to occur then were delayed. However, timing factors that help in one quarter can hurt in the next quarter. Expect higher expenses when Illumina reports its results next week.

The launch of Helix, Illumina's consumer genomics venture, in the third quarter will certainly be one factor behind an increase in operating expenses. However, Illumina also planned to boost some other investments in the back half of 2017 after its second-quarter revenue turned out so strong.

3. News on Helix

Speaking of Helix, expect Illumina's executives to, well, speak of Helix a good bit in the third-quarter update. When Illumina last reported quarterly results, Helix had launched its online marketplace only a few weeks earlier. That launch included over 20 products and services, from ancestry DNA testing to wine recommendations based on customers' DNA.

So far this year, Helix hasn't impacted Illumina's financial performance very much positively or negatively. As with any launch, expect more expenses than revenue at the beginning. Don't count on big news from Helix just yet. However, Illumina CFO Marc Stapley stated in August that "2018 will certainly be an interesting year" for the consumer genomics unit. Stay tuned.

Regardless of what Illumina reports

I fully expect Illumina to have another great quarter. However, there's a chance that the company will miss analysts' estimates. It could take longer for academic customers to get funding for NovaSeq than expected. Some of that lumpiness in consumables revenue mentioned by Rebecca Chambers as customers transition from older systems to NovaSeq could be a factor.

Regardless of what Illumina's third-quarter numbers are, though, the underlying investing premise for the stock should remain intact. The company's recurring revenue is enormous. There's a large untapped market for NovaSeq. And Illumina's moat isn't likely to be breached, with the company continuing to invest heavily in research and development. Illumina's third quarter could be great, but it might not be. But the long-term prospects for the gene-sequencing pioneer still appear to be bright.

Keith Speights has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Illumina. The Motley Fool has a disclosure policy.