For HCUP data from 2001 to 2002, this data element is called MDNUM2_S. Beginning in 2003, this data element is called MDNUM2_R.

SURGID_S contains a fixed-key (one-to-one) encryption of the supplied primary surgeon number (SURGID), according to the following rules:

• All alphanumeric digits are used in the encryption.
• All symbols such as ".,:;'*@" are retained in the encrypted value, but not in the same location.
• Leading zeros are encrypted so that the two original physician identifiers "000A6" and "A6" are distinctly different.
• When the original attending physician and primary surgeon identifiers are the same, the synthetic identifiers, MDID_S and SURGID_S, are the same.
• When the SURGID in the ambulatory surgery data and the inpatient data are the same, the synthetic identifier, SURGID_S is the same.

Except in those data sources where physician license numbers are supplied, it is not known whether the physician identifier SURGID_S refers to individual physicians or to groups. If the primary surgeon numbers supplied by the data source are not restricted to license numbers, the state-specific note includes available information about reporting practices, including whether SURGID_S refers to individual physicians or to groups.

Beginning in the 1993 data, supplied physician identifiers were checked for null characters. If null characters were found, they were replaced by blanks before the identifier was encrypted. Since this conversion was not done in prior years of HCUP data, the encrypted physician identifiers from 1993 on may not match those in earlier years. However, null characters are rarely included.

Beginning with 1993 NIS, supplied surgeon identifiers were checked for null characters. If null characters were found, they were replaced by blanks before the identifier was encrypted. Since this conversion was not done in prior years of HCUP inpatient data, the encrypted surgeon identifiers from 1993 on may not match those in earlier years. However, no null characters were found in the 1994 identifiers, and they were rare in prior years.

The identification number for primary surgeons (SURGID_S) may not accurately track physicians across hospitals for the following reasons:

• Some hospitals assign their own internal other physician identification numbers rather than using the license numbers issued by the licensing agency of the physician or other health care practitioner. Information was not available about the prevalence of this practice.
• Some hospitals use one identification number for several physicians that are part of the same physician practice group. Information was not available about the prevalence of this practice.

Arizona's identification number for primary surgeons includes license numbers from the following board of examiners: Medical, Osteopathic, Podiatrists, and Nurses. In addition, Arizona accepts licensing numbers from other health practitioner licensing boards, but these boards are unspecified.

The primary surgeon number (SURGID_S) may not accurately track physicians across hospitals. The state encourages hospitals to use the Professional State License Number as an identifier, but some hospitals continue to use their own internal identification number. Also, some hospitals appear to pad the Professional State License Number (a 5-digit code). Information was not available from the data source about the prevalence of these practices.

Some hospitals may use one license number for all physicians in order to protect physician confidentiality. Information was not available about the prevalence of this practice.

Prior to 2000, Connecticut provided professional state license numbers as physician identifiers and supplied encrypted primary surgeon identifiers to HCUP. During HCUP processing, physician identifiers were re-encrypted (SURGID_S).

Source documentation indicates that if a physician does not have a number (i.e., they are from out of state or a resident at the hospital), then the hospital can assign a separate identifying number. Beginning in 2000, Connecticut does not provide physician identifiers to HCUP.

Florida reports state license numbers for the operating physician identifiers. During HCUP processing, physician identifiers were encrypted (SURGID_S).

It is possible that two different values of SURGID_S identify the same physician. Either the physician's state license number or the Universal Physician Identification Number (UPIN) is used to identify the first other physician.

Beginning in 1998, the variable SURGIDTYPE identifies whether the physician identifier is a state license number (SURGIDTYPE = "S") or UPIN (SURGIDTYPE = "U").

During HCUP data processing, the source provided physician identifier is encrypted to create SURGID_S.

Beginning in 1995, MDID and SURGID are not available from the source. MDID_S and SURGID_S are missing for all records.

From October 1991 to December 1994, it is possible that two different values of SURGID_S identify the same physician. For discharges involving Medicare or Medicaid payers either the physician's license number or the Universal Physician Identification Number (UPIN) could have been reported. The IHCCCC reports that use of UPINs for physician identifiers is hospital-specific and may change over time. UPIN is required for all other payers.

Beginning in 1994, Iowa reports a principal physician ID (SURGID_S) in addition to the attending physician ID (MDID_S).

Iowa reports Universal Physician Identification Numbers (UPINs) as physician identification numbers.

The encrypted identifier for the physician performing the principal procedure (SURGID_S) may not accurately track physicians across hospitals. Kentucky collects two different types of physician identifiers, Universal Physician Identification Numbers (UPINs) and state license numbers.

Maine provides state-specific encrypted physician identifiers for operating surgeons that allow for tracking physicians across hospitals.

Caution should be used when tracking physicians back to 1999. The encrypted values supplied by the source in the 1999 inpatient data contained slightly different coding than the values supplied in the 1999 outpatient and 2000 inpatient data. During HCUP processing, physician identifiers were re-encrypted (SURGID_S).

Maryland reports a state license number assigned by the Medical Chirurgical Faculty of Maryland (MED CHI) for the attending physician. Source documentation describes strict assignment and verification rules for this field.

Massachusetts reports encrypted Massachusetts Board of Registration in Medicine's license number for the operating physician.

Michigan reports hospital-specific physician identifiers for the surgeon. Coding of physician identifiers are not consistent across hospitals. During HCUP processing, physician identifiers were encrypted (SURGID_S).

The primary surgeon identification number (SURGID_S) may not accurately track physicians across hospitals. Missouri accepts Universal Physician Identification Numbers (UPINs), state license numbers, and hospital-assigned physician identification numbers as primary surgeon numbers. According to the source, the majority of physician identifiers are UPINs.

The coding of primary surgeon identification number (SURGID_S) varies across years:

New York reports state license numbers as physician identifiers. Source documentation indicates that if the operating physician did not possess a valid New York state license number, the license number of the operating physician or Chief of Service should have been reported.

New York does not limit this field to physicians; dentists, podiatrists, psychologists, nurse/midwifes, and other licensed health care professionals may be included. It is impossible to identify the different types of providers in the HCUP data.

Source physician identifiers are encrypted during HCUP processing.

For 1998 - 2000, physician identifiers are missing (" ") on discharges with an indication of an induced abortion. New York identifies an indication of induced abortion by ICD-9-CM diagnosis or procedure code:

• An admitting, principal, or secondary diagnosis of "6350" through "6399", or "7796".
• A principal or secondary procedure of "690", "695", "696", "6993", "738", "7491", "750", "751", or "9649".

Please note that the admitting diagnosis is not retained in the HCUP databases.

North Carolina provides the Universal Physician Identification Number (UPINs) for the 1st other physician. During HCUP processing, this identifier is encrypted.

An identifier for the 1st Other Physician was provided by Oregon and encrypted during HCUP processing (SURGID_S). This identifier may not accurately track physicians across hospitals. Oregon encourages hospitals to use Universal Physician Identification Numbers (UPINs), but not all hospitals do. Information was not available from the data source about the prevalence of this practice.

Pennsylvania reports the PA state license number for the operating physician.

South Carolina reports six-character state license numbers for other physician identifiers. When the source values were shorter than six characters, the HCUP value was padded to bring it into conformity with South Carolina's format before the value was encrypted.

The encrypted identification number for the first other physician is retained in SURGID_S. SURGID_S may not accurately track physicians across hospitals. Tennessee collects two different types of physician identifiers, depending on the type of identifier provided by the hospitals. Tennessee prefers Universal Physician Identification Numbers (UPINs) but also accepts state license numbers. If neither identification number is available, SURGID_S is missing (SURGID_S = blank).

Texas provides the state license number of the operating physician. During HCUP processing, physician identifiers were re-encrypted (SURGID_S).

Prior to 1999, an error in the supplied surgeon identifier required that SURGID and SURGID_S be set to blank on all records. Beginning in 1999, SURGID and SURGID_S are coded. It is possible that two different values identify the same surgeon. Utah reports a mixture of state license numbers and hospital-specific internal physician identifiers.

Virginia reports the physician performing first procedure using Universal Physician Identification Numbers (UPINs) for the physician that performed the first procedure. During HCUP processing, physician identifiers were encrypted (SURGID_S).

Washington reports this identifier as "Other Physician ID" which can refer to any physician who performs the procedure, not just a surgeon.

The Washington physician identifiers may not accurately track physicians across hospitals. Washington collects several different types of physician identifiers, depending on the type of identifier provided by the hospitals. Hospitals provide Medicaid, Universal Physician Identification Numbers (UPINs), and DOH/HPQAD license numbers as physician identifiers. During HCUP processing, physician identifiers were re-encrypted (SURGID_S).

The encrypted other physician identifier (SURGID_S) may not accurately track physicians across patients and hospitals. West Virginia collects different types of physician identifiers depending on the payer:

• The Universal Physician Identification Numbers (UPINs) are coded on Medicare patients.
• A West Virginia Medicaid physician identifier is coded on Medicaid patients. The same physician treating two different Medicaid patients can have two different physician identifiers. One identifier is used for new Medicaid patients; the other identifier is used for established Medicaid patients.
• The physician's state license number is coded on most commercial patients. Some hospitals use their own physician identifiers and do not provide the UPIN, Medicaid and state license numbers.