The Centers for Medicare & Medicaid Services is  scheduled to reveal overall star ratings for hospital quality on April 21, but 60 senators have urged the agency to delay the release amid concerns about allegedly incomplete and misleading data. It is unknown how much of this call for delay is due to political pressures from hospitals in the senators’ home states.

In a letter to Acting CMS Administrator Andy Slavitt, the senators say that flawed quality measures can cause wide variations between CMS’s quality ratings and other reports.

The senators added: “It is clear that additional time is necessary for hospitals and stakeholders to thoroughly review the data and understand the impact of the current methodology to ensure the validity and accuracy of the information before it is publicly released,” the letter states.

They also expressed concerns that the ratings methodology didn’t properly include providers that treat low-income or disadvantaged patients.

The star ratings and the methodology used for them have long been a source of controversy.