(Adds estimates, share movement)
April 20 (Reuters) - Abbott Laboratories fell short of first-quarter revenue estimates on Tuesday, suggesting that the medical device maker may be facing slowing sales of its COVID-19 test kits as vaccinations gain steam.
In the quarter, COVID-19 test kits generated sales of $2.2 billion and accounted for more than half of the diagnostic unit's revenue. But that compared with $2.4 billion in the prior quarter.
Abbott's shares fell 3% to $120.67 in trading before the bell.
Rival Quest Diagnostics, which is set to report its quarterly results on April 22, said in February that it was expecting demand for its COVID-19 tests to shrink in the year as vaccination efforts ramp up.
Abbott, Quest and Becton Dickinson and Co benefited from heightened COVID-19 testing during the early phase of the crisis, a revenue stream that helped blunt the blow from lower demand for medical devices.
Net sales at Abbott increased to $10.5 billion, but fell short of estimates of $10.7 billion, according to IBES data from Refinitiv.
The company reiterated its 2021 adjusted diluted earnings per share outlook of at least $5.00. Excluding items, the company earned $1.32 per share, above the average analyst estimate of $1.27.
(Reporting by Amruta Khandekar and Mrinalika Roy in Bengaluru; Editing by Sriraj Kalluvila)
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