In the last trading session, the U.S. stocks managed to hold on to modest gains in what was overall a rocky session. Among the top ETFs, investors saw (SPY –ETF report) gain 0.09% while (DIA – ETF report) and (QQQ – ETF report) move higher by 0.2% on the day.

Two more specialized ETFs are worth noting as both saw trading volume that was far outside of normal. In fact, both these funds experienced volume levels that were more than double their average for the most recent trading session. This could make these ETFs ones to watch out for in the days ahead to see if this trend of extra-interest continues:

(PTH – ETF report): Volume 6.18 times average

This healthcare ETF was in focus yesterday as around 348,000 shares moved hands compared with an average of roughly 61,000 shares. We also saw some price movement as PTH lost 0.2% in the last session.

The big move was largely the result of investors' rush for bargain hunting after last week's biotech sell-off that can have a big impact on the healthcare stocks like what we find in this ETF portfolio. In the past one-month period, PTH was down nearly 14.8%. The fund has a Zacks ETF Rank of 3 or ‘Hold' rating with a High risk outlook.

(BIL – ETF report): Volume 4.35 times average

This short-term Treasury ETF was under the microscope yesterday as more than 6.4 million shares moved hands. This compares with an average trading day of around 1.6 million shares and came although BIL remained unchanged at the close in the session.

The movement can largely be blamed on the latest Fed minutes that have dampened the prospect of a rates hike anytime soon and rekindled investors' interest in the bond space. This is because lower rates will push the yields down, boosting the prices for the bonds. BIL delivered flat returns in the past one month and currently has a Zacks ETF Rank of 3 with a Low risk outlook.

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