Content » Vol 95, Issue 3

Short communication

Trichomonas vaginalis Infections are Rare Among Young Patients Attending an STI Clinic in Sweden

Helena Pellrud1, Daniel Golparian2, Christian Steczkó Nilsson1, My Falk1, Hans Fredlund2 and Magnus Unemo2*

1STD Clinic, Department of Dermatovenereology, Örebro University Hospital, Örebro, and 2WHO Collaborating Centre for Gonorrhoea and other Sexually Transmitted Infections, Swedish Reference Laboratory for Pathogenic Neisseria, Department of Laboratory Medicine, Clinical Microbiology, Örebro University Hospital, Örebro, Sweden. *E-mail:

Accepted Aug 19, 2014; Epub ahead of print Aug 19

Trichomonas vaginalis infections represent the most common curable non-viral sexually transmitted infection (STI) worldwide. In 2008, 276 million incident cases of T. vaginalis infections were estimated by the WHO among adults (36–45 years of age) globally (1). Trichomoniasis may cause vulvar irritation with purulent or frothy white-to-yellow malodorous discharge, dysuria, pelvic pain and itching in women, and urethral discharge, dysuria and testicular pain in men. The infection may be asymptomatic in 50% of infected women and 70–80% of infected men (2–4). T. vaginalis infections have been associated with pelvic inflammatory disease, adverse outcomes of pregnancy (low birth weight and premature birth) and increased risk of HIV transmission and acquisition (2–6).

For diagnosis of trichomoniasis, microscopic examination of a wet-mount preparation of vaginal secretions is the most frequently used method internationally. If appropriately performed by an experienced microscopist, the specificity can be high; however, the sensitivity is suboptimal, i.e. in comparison with nucleic acid amplification tests (NAATs) 44–68% in women and even lower in men (2, 7–9). In-house culture or, e.g. the commercial InPouch TV culture system (BioMed Diagnostics, White City, USA), have a higher sensitivity; however, this method requires 5–7 days for completion and is rarely used in many settings (2, 7, 8). Several in-house NAATs that offer improved sensitivity for detection of T. vaginalis have been developed (2). Recently, the first NAAT for diagnosis of trichomoniasis was approved by the United States Food and Drug Administration (FDA), i.e. the APTIMA T. vaginalis assay (Hologic, San Diego, USA). This NAAT has superior sensitivity compared with traditional diagnostic methods (2, 8–11) and the clinical sensitivity and specificity have been stated to be >95% and 98%, respectively (12). Using this NAAT, studies from the USA have shown prevalences of T. vaginalis in STI populations of 10–12% and in the general population of 3% (6, 10–14). In Sweden, mainly wet-mount micro­scopy solely is used for detection of T. vaginalis and the prevalence of trichomoniasis has never been evaluated with a highly sensitive and specific NAAT.

The aim of this study was to investigate the prevalence of T. vaginalis infections among patients attending an STI clinic in Sweden using the APTIMA T. vaginalis assay.


All consecutive patients (n = 1,121) attending the STI clinic at the Örebro University Hospital, Örebro, Sweden from May 2012 to January 2013 were enrolled in the study after giving their written consent. The patients attended the STI clinic due to complaints indicating an STI, sexual contact tracing, or being concerned about infection having had unprotected sex. Specimens were collected from all patients in the APTIMA sampling medium (Hologic) and were subsequently tested with the APTIMA T. vaginalis assay (Hologic) on the PANTHER platform (Hologic), in accordance with the instructions from the manufacturer. All women also underwent gynaecological examination, when vaginal specimens were collected for wet-mount microscopy. The study protocol was approved by the ethics committee of Uppsala University, Sweden (Dnr 2012/249).


During the study period, urine specimens from 501 males and 460 females, and vaginal swabs from additional 160 females were collected. The mean age of the females and males was 28 years (median age 26 years; range 15–62 years) and 32 years (median age 30 years; range 18–77 years), respectively. The age distribution of the patients is shown in Fig. 1.


Fig. 1. Age distribution of females and males attending a Swedish sexually transmitted infections (STI) clinic and tested for Trichomonas vaginalis in the present study.

Only one specimen positive in the APTIMA T. vaginalis assay was identified, and the prevalence of T. vaginalis infection was, accordingly, 0.09% (0.16% among the females and 0% among the males) in this young STI population in Sweden. The positive patient was a 38-year-old Swedish Caucasian female with only 2 sexual contacts in the previous 6 months (both in Sweden). She had symptomatic trichomoniasis and was also positive in the wet-mount microscopy. No additional positive female was found by wet-mount microscopy. For comparison, the prevalence of bacterial vaginosis and Chlamydia trachomatis infection of the investigated females was 10% and 6.6%, respectively.


The present study is the first assessment of the prevalence of T. vaginalis infection in the patients attending a regional STI clinic in Sweden using a highly sensitive and specific NAAT, i.e. the FDA-approved APTIMA T. vaginalis assay (Hologic; 2, 5, 8–11). Although T. vaginalis infections are common in many settings internationally (1, 2, 6, 10–14), they appear to be rare among young patients attending an STI clinic in Sweden. T. vaginalis infections have previously been highly associated with higher age of females (peaking at between 40 and 50 years of age) as well as with ethnicity, i.e. black race (2, 6, 10–14). In particular, this difference in age distribution is relevant to informing STI control programmes and appropriate targeting of screening efforts. In the present study, only 9% of the females were more than 40 years of age and ethnicity was not adequately recorded. Notably, the only T. vaginalis positive specimen in the present study was from one of the few slightly older females (38 years of age). Thus, the limitations of this study were the low number of women ≥ 40 years and the lack of appropriate recording of ethnicity. Additional studies are crucial to address those issues and provide evidence-based data regarding the prevalence of T. vaginalis infections in the population of Sweden as well as in many other countries.


The study was supported by grants from the Örebro County Council Research Committee and the Foundation for Medical Research at Örebro University Hospital, Sweden. APTIMA T. vaginalis tests were provided by Hologic, San Diego, CA, USA.

The authors declare no conflicts of interest.


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