Stocks galloped ahead Thursday as the market's condition switched to a confirmed uptrend.

The Nasdaq staked a 1.4% gain, its best price pop since Jan. 22. The S&P 500 and the Dow Jones industrial average chipped in gains of 1.1% each.

The IBD 50 rose 1.4%.

Volume fell on the NYSE but rose about 4% on the Nasdaq.

A follow-through day, which signals a new uptrend underway, involves a sizable price gain in a major index. Volume must be up from the previous day.

The Nasdaq met those requirements, though volume rose against an easy comparison.

While individual investors might be tempted to scoff at such a follow-through, there's a better way to react: Don't assume, but conduct a test.

Find a quality stock that is breaking out, open a half position and see if the stock's action justifies completing the full position.

The standard method is a half position as close as possible to the ideal entry; a second buy of 30% of shares if the stock rises 2% or 3%; and a final 20% buy if it rises another 2%.

If the breakout works, then look for another stock to buy.

If the breakout stalls, don't complete the full buy, and unwind the position or give it more time. When a stock isn't working, an investor might want to exit before the loss reaches 8%.

Never allow a loss to grow beyond 8%.

On Thursday, e-commerce ad products provider Criteo (NASDAQ:CRTO) broke out of a 16%-deep pattern. The stock cleared a 46.60 buy point in strong volume.

Criteo is a fast grower. Its client base was 350 in eight countries in 2010. As of December, the client count was 7,190 in 69 countries. Torrid hiring, though, is expected to slow earnings growth from 359% last year to 2% this year.

The Street expects earnings growth of 36% in 2016.

Stocks that break out soon after a follow-through day should be considered for purchase. Research shows that the early breakouts sometimes become the leaders of a new uptrend.

Quality breakouts were scarce Thursday, but a number of top-rated stocks reclaimed their 50-day moving averages. This accomplishment, while modest, is necessary if a stock is to climb the right side of a pattern and break out.

Stocks retaking the 50-day line included Apple (NASDAQ:AAPL), Facebook (NASDAQ:FB), Middleby (NASDAQ:MIDD), Prestige Brands (NYSE:PBH) and Hilton Worldwide (NYSE:HLT).

In economic news, first-time jobless claims were 4% lower than expected, a bullish sign. However, the Producer Price Index for April fell 0.4%, vs. views for an 0.2% gain.