Concept: Syphilis - Method of Identification

Introduction

This concept provides a working definition of syphilis and describes the methods used at MCHP to investigate syphilis in the administrative data held in the Manitoba Population Research Data Repository. The concept lists the ICD-9-CM and ICD-10-CA diagnostic codes to identify syphilis in the hospital abstracts data and the medical services data, and lists the codes that are used in laboratory tests to investigate its presence in the population. SAS code (internal access only) is also available for working with the laboratory data.

Definition of Syphilis

Syphilis is primarily a sexually transmitted infection (STI) caused by the spirochete bacterium Treponema pallidum. There are five stages to classify syphilis: primary, secondary, early latent, late latent, and tertiary. These stages reflect the progression of the infection and the communicability of the disease (Public Health Agency of Canada Website - Notifiable Diseases On-Line - Syphilis). Transmission is more probable during primary, secondary, and early latent stages. During these periods, the estimated risk of communicability is 60% per partner (Manitoba Health - Communicable Disease Control Unit - Communicable Disease Management Protocol - Syphilis). Symptoms can occur within a few weeks or a couple of months after infection. The first symptom may be a painless, open sore or ulcer where the bacteria first entered the body. Later symptoms include patchy hair loss, rash on soles of the feet or palms of the hands, fever, swollen glands, and muscle and joint pain. Symptoms usually disappear without treatment. If left untreated, syphilis can affect the brain, blood vessels, heart, and bones, and can eventually lead to death.

Transmission of syphilis may also occur transplacentally from an untreated mother to the fetus or through the birth canal when the newborn infant contacts a genital lesion. Congenital transmission occurs predominantly when the mother is in the primary or secondary stage of infection. Although much less common, syphilis may also be transmitted though sharing of contaminated needles among injection drug users (Manitoba Health - Communicable Disease Control Unit - Communicable Disease Management Protocol - Syphilis).

Because of the significant public health implications, syphilis is a notifiable disease in Canada since 1924 (Lix et al., 2012). All positive laboratory-confirmed cases of syphilis are reportable by laboratory operators and health care professionals to the Communicable Disease Control Unit of Manitoba Health.

MCHP Syphilis Algorithms

The following two methods have been used at MCHP to determine testing and to identify individuals with syphilis.

1. Brownell et al. (2012)

In Brownell et al. (2012), a Manitoba Health Report on the provincial count of syphilis by age and sex distribution for the year 2010 was examined (Manitoba Health - Epidemiology and Surveillance - Monthly Communicable Disease Reports / Manitoba Monthly Surveillance Unit Reports - 2010). This report indicates the number of reported cases of infectious or noninfectious syphilis as well as those that required additional follow up to confirm their status. For youths aged 15 to 19 years, two cases of syphilis for females were identified and none for males. For youths aged 10 to 14 years, there was one case for females and two for males. Thus, the small numbers preclude presentation by region or income quintile. For more information read the section titled Syphilis in Brownell et al. (2012) .

2. Lix et al. (2012)

In Lix et al. (2012), the Cadham Provincial Laboratory (CPL) data from 1992/93 to 2008/09 was used to identify the total number of syphilis tests and the frequency of positive tests (laboratory-confirmed cases) by fiscal year in Manitoba. Less than 3% of all syphilis tests were positive in each of the study years.

Data from the CPL Serology Section was used to identify the CPL number of syphilis tests and the frequency of positive laboratory-confirmed cases in Manitoba. The serologic tests are used to detect antibodies formed during the course of the bacterial infection. Two types of clinical serologic tests for syphilis are performed at CPL: nonspecific nontreponemal antibody tests and specific treponemal antibody tests. Both tests are essential to establish a diagnosis of syphilis (Manitoba Health - Communicable Disease Control Unit - Communicable Disease Management Protocol - Syphilis).

Table 1 reports the AUXCD5 codes used to identify syphilis testing in the Serology Section of CPL. For more information on CPL, see the CADHAM Provincial Laboratory (CPL) - Overview of Services and Data concept.

NOTE: On rare occasions a negative serologic result may be determined in an active syphilis case, particularly in older patients or during an early primary infection (Manitoba Health - Communicable Disease Control Unit - Communicable Disease Management Protocol - Syphilis).

Table 1 - Syphilis: Serology Section

STARTDT 1	STOPDT 2	AUXCD5	DESCR40
12/2/1993	1/1/2099	ARPR	SYPHILIS SCREEN
12/2/1993	1/1/2099	CONF	SYPHILIS CONFIRMATORY
1/1/1990	1/1/2099	DFA	SYPHILIS DIRECT EXAM
1/25/2002	2/29/2007	DFAR	SYPHILIS DIRECT FLUORESCENT ANTIBODY
1/1/1990	12/3/1993	FTABS	SYPHILIS REFERENCE
1/1/1990	12/3/1993	IGM	SYPHILIS IGM
1/1/1990	12/3/1993	MHATP	SYPHILIS CONFIRMATORY
12/2/1993	1/1/2099	REF	SYPHILIS REFERENCE
1/1/1990	12/3/1993	RPR	SYPHILIS SCREEN
12/2/1993	5/1/2006	SIGM	SYPHILIS IGM
1/1/1990	1/1/2099	SYRPR	SYPHILIS SCREEN
1/1/1990	12/3/1993	VDRL	SYPHILIS QUANTITATIVE
12/02/93	01/01/99	BVDRL	SYPHILIS QUANTITATIVE


¹ - The date that the code was created in the file.
² - The date that the code became inactive.

Comparison of Lab Data to Hospital Discharge Abstracts and Medical Services Data

Syphilis diagnoses from the hospital abstracts data and the medical services data were compared to the CPL data. ICD-9-CM codes 090-097 and ICD-10-CA codes A50-A54 were used to identify the diagnoses of syphilis. Approximately 30% of positive tests (laboratory-confirmed cases) for syphilis had a corresponding diagnosis in either hospital abstracts or medical services data 180 days before or after the index date. For more information on how syphilis was investigated in the CPL data, read the section titled Case Study #3: Sexually Transmitted Infection Tests in CPL Data and Sexually Transmitted Infection Diagnoses in Hospital and Physician Billing Records in Lix et al. (2012) .

SAS Code

SAS code for identifying syphilis tests in the Cadham Provincial Laboratory data is available in the SAS code and formats section below (internal access only).

Limitations /Cautious

• Cadham Provincial Laboratory performs virtually all clinical serologic testing and screening for syphilis in Manitoba, but laboratory data may not capture all cases in a jurisdiction.
  
  
• The technology for testing various STI or STBBIs has changed over the last several years; therefore examining trends in these infections may not reflect actual trends in the infections themselves but changes in detection. For this reason, syphilis was examined not over time but for a single year in Brownell et al. (2012) .
  
  
• A value of P [Positive] to identify a positive test result in the POSNEG field [Positive-Negative] for specific AUXCD5 codes in the CPL data was used to determine a positive test result.
  
  
• The AUXCD5 codes used to identify syphilis in the Serology Section should be verified at the beginning of each new study to ensure they are up-to-date.