ATLANTA--CMS closed down its new Internet registry of National Provider Identification numbers last week because of "recent instability," the agency said.

The registry, which was developed as a resource to providers submitting Medicare claims, is expected to be back in operation sometime this week, CMS said in a statement. The agency had initially announced that it would take down the NPI Registry for one day only on Sept. 18. Friday's announcement extended the period.

"Many of you have noted the recent instability of [The National Plan and Provider Enumeration System] and the NPI Registry," CMS said in its notice. "CMS has begun implementing changes that should eliminate the instability. We expect that these changes will be completed next week. NPPES will remain in operation while these changes are being made, but the NPI Registry will remain down until all changes have been implemented. We expect the NPI Registry to be back in operation sometime next week. We apologize for the inconvenience."

The registry allows health care providers to locate their referral sources' NPI numbers for the purpose of submitting Medicare-compliant claims.

While some providers said they did indeed find it helpful, according to others, the system, which debuted Sept. 4, contains a troubling issue: It also reveals National Supplier Clearinghouse identification numbers, which could allow access to a provider's proprietary information (see HomeCare Monday, Sept. 17).

A spokesman for CMS said that furnishing the NSC numbers was optional. "Providers can remove their NSC numbers from NPPES whenever they wish. Once they remove them, those numbers will not appear in the NPI Registry because the NPI Registry is a 'real time' system," the spokesman said.

However, CMS did not respond to a question about what effect removing an NSC number from the NPI registry would have on verifying the NPI-legacy number pairs currently necessary for claims payment.