Who cares for syphilis? A cross-sectional study on diagnosis and treatment of syphilis by GPs in Amsterdam, the Netherlands

Article Figures & Data

Download figure
Open in new tab
Download powerpoint
Figure 1. Exclusion of tests and number of remaining tests, requests and patients.
Download figure
Open in new tab
Download powerpoint
Figure 2. Annual number of lab requests and positivity rates in men and women. Positivity rate: number of syphilis diagnoses per number of lab requests. One lab request was defined as all laboratory tests in the same patient within a timeframe of 30 days.
Download figure
Open in new tab
Download powerpoint
Figure 3. GPs and STI clinic syphilis diagnoses in Amsterdam. The number of syphilis diagnoses in Amsterdam between 2011 and 2017, shown for GPs and STI clinic. GPs’ contribution based on the extrapolated estimated 90% coverage of all GPs laboratory data in Amsterdam, with 80% and 100% coverage estimates as levels of uncertainty. STI = Sexually transmitted infection.
Download figure
Open in new tab
Download powerpoint
Figure 4. Potential syphilis cases and treatment of cases in general practice, separated by site of diagnosis. *Based on the stage of disease the first choice treatment of syphilis consists of one or three penicillin injections. Undertreated is when one penicillin injection was given when three were recommended by the guideline, and vice versa for overtreated. ICPC = International Classification of Primary Care. STI = sexually transmitted infection.

Table 1. Laboratory syphilis tests

Characteristic	Patients tested n =52 055	Syphilis diagnoses n = 522 (positivity %)	Laboratory tests n =67 953	Positive laboratory tests n =6503
Sex
Male	28 090 (54.0)	501 (1.8)	39 060 (57.5)	5591 (14.3)
Female	23 963 (46.0)	21 (0.1)	28 891 (42.5)	912 (3.2)
Missing data	2	0	2	0
Age years, ^a median ( IQR )	34 (27–44)	44 (35–52)
<15	132 (0.3)	0	151 (0.2)	0
15–25	8478 (16.3)	33 (0.4)	9881 (14.5)	262 (2.7)
26–35	20 549 (39.5)	103 (0.5)	25 074 (36.9)	951 (3.8)
36–45	11 641 (22.4)	156 (1.3)	15 393 (22.7)	1649 (10.7)
46–55	7031 (13.5)	153 (2.2)	10 630 (15.6)	2050 (19.3)
>55	4213 (8.1)	77 (1.8)	6824 (10.0)	1591 (23.3)
PCR	N/A	N/A	617 (0.9)	106 (17.2)
Anti- T. Pallidum ( EIA )	N/A	N/A	46 389 (68.3)	3095 (6.7)
Positive in the past^b	N/A	N/A	N/A	1303 (42.1)
New positive^c	N/A	N/A	N/A	85 (2.7)
TPHA/TPPA	N/A	N/A	17 125 (25.2)	1842 (10.8)
Positive in the past^b	N/A	N/A	N/A	607 (33.0)
New positive^c	N/A	N/A	N/A	30 (1.6)
Confirmation (immunoblot)	N/A	N/A	1042 (1.5)	926 (88.9)
VDRL/RPR (positive ≥1:4)	N/A	N/A	2780 (4.1)	534 (19.2)

^aAge in years at first test for patients’ column, age at test for other columns. ^bSome laboratories reported laboratory tests as 'positive in the past', even though it was the first lab request in this patient during the studied period. ^c New positive after an earlier negative test.
EIA = enzyme immunoassay. IQR = interquartile range. N/A = not applicable. PCR = polymerase chain reaction. RPR = rapid plasma reagin. TPHA/TPPA = Treponema pallidum haemagglutination assay/T. pallidum particle agglutination assay.VDRL = venereal disease research laboratory.

Table 2. Characteristics of syphilis cases in general practice (n = 43)

Characteristic	Frequency, n (%)
Sex
Male	36 (84)
Female	7 (16)
Age, years
16–25	11 (26)
26–35	7 (16)
36–45	7 (16)
46–55	8 (19)
>55	10 (23)
(Half) Year of diagnosis
1 July 2013–31 Dec 2013	5 (12)
2014	10 (23)
2015	9 (21)
2016	11 (26)
2017	8 (19)
1 Jan 2018–31 July 2018	0
HIV status
Positive	8 (19)
Co-infection	3 (7)
Not recorded	32 (74)
Stage of disease
Primary	10 (23)
Secondary	6 (14)
Early latent	3 (7)
Late latent	6 (14)
Neurosyphilis	0
Unknown^a	17 (40)
Missing data	1 (2)
Follow-up	39 (91)
Missing data	4 (9)
Referral	6 (15)
Sexually transmitted infection clinic	3 (50)
Venereologist or internist	3 (50)
Treated by GP	33 (85)
1x penicillin	18 (55)
3x penicillin	15 (45)
According to guideline ^b	28 (85)
Undertreated	3 (9)
Overtreated	2 (6)

^aUnknown stage of disease or possible serological scar, which is clinically the same as late latent stage and requires 3x penicillin treatment.^b Based on the stage of disease the first choice treatment of syphilis consists of one or three penicillin injections. Undertreated is when one penicillin injection was given when three were recommended by the guideline, and vice versa for overtreated.