Try this multiple-choice quiz: Which is the commonest venerealdisease in industrialized countries? (a) Gonorrhea (b) Genital herpes(c) Syphilis (d) Chlamydiosis (e) AIDS
The answer is (d). Four million people a year in the U.S. alone arediagnosed with genital infection by the Chlamydia trachomatisbacterium.
In men, the pathogen causes symptoms similar to those of gonorrhea.But fully 70 percent of infected women have no symptoms at all.This unawareness exposes them to such chlamydial depredations aspelvic inflammatory disease, ectopic pregnancies and infertility. Astheir babies pass through the birth canal, they often pick up thelurking C. trachomatis, which may leave them with blinding eyedisease or pneumonia.
And unwittingly, asymptomatic women may pass on the infection totheir sexual partners. Among sexually active teenagers, an estimatedone in seven girls and one in 12 boys are infected with chlamydia.
At present, diagnosing a women for possible chlamydiosis involves apelvic examination, which includes the process of swabbing thecervical area to collect a testable sample.
Moreover, said bacteriologist Helen Lee, "five to 30 percent areinfected only in the urethra, which lies beyond the cervical swab."
Lee is general manager of the Probe Diagnostic Business Unit atAbbott Laboratories, in Abbott Park, Ill. She and her group have justdevised and clinically tested a simple urine test for genitalchlamydiosis, and reported it in this week's Lancet, dated Jan. 28.
The paper, of which she is first author, bears the title: "Diagnosis ofChlamydia trachomatis genitourinary infection in women by ligasechain reaction of urine."
"The Lancet article is important," Lee told BioWorld Today, "inlarge part due to the fact that prior to ligase chain reaction (LCR),female urine testing had not been possible." She explained that "LCRis similar to PCR [polymerase chain reaction] in that it is also aDNA-amplification technology. But the way we get at it is differentfrom PCR."
LCR's main advantages, Lee added, are "that it is much moreappropriate and efficient in finding point mutations, as well as givingtremendous sensitivity and specificity." To obtain these features, theAbbott team takes as the target sequence complementary to itsprobes a "cryptic plasmid," of which C. trachomatis harbors seven to10 copies in its genome.
"The application of LCR technology in clinically relevant tests isnew," Lee observed. "When we do have this chlamydia urine test, itwill be the first LCR product available."
That time could be quite soon. The company is awaiting FDAmarketing approval, based on its pivotal trial described in TheLancet.
Having previously ascertained the urine test's reliability in males,(who are painfully aware of their symptoms), Lee's team lined upfour clinical centers, three American, one Canadian, for self-controlled trials of LCR-tested urine samples vs. endocervical swabs,both from the same 1,937 women. LCR correctly called 93.8 percentof the infected women, versus only 65.0 percent by the swabs.
"In the U.S., unlike some Scandinavian countries," Lee observed,"we only test endocervical swabs. Therefore, by definition, we donot detect the urethra-only infection."
Chlamydiosis costs the U.S. economy upwards of $2 billion a year,she said. "This covers mainly the hospitalization of pelvicinflammatory disease patients, each of which costs in the thousandsof dollars. Diagnostics is a small part of the total cost to the healthcare system."
She added, "Detection is really the way to go; recognize the reservoirof infected individuals, together with appropriate treatment, byinexpensive and cost-effective antibiotics."
Lee and her team are now extending their LCR-urine test to "anumber of other infectious diseases, beginning with tuberculosis. "InTB," she said, "culture of the pathogen takes six to eight weeks tocomplete. Our LCR sputum test can have an answer the same day."
In an editorial accompanying the Lancet article, Edinburghgenitourinary specialist Gordon Scott found the LCR urine testlacking: "The opportunity to diagnose other sexually transmitteddiseases . . . during vaginal/pelvic examinations will be lost," hesaid.
To which Lee responded: "In the context of chlamydiosis, if you tiethe detecting to a pelvic exam, you're not going to get at the largereservoir of asymptomatic women, who may not come in for a pelviccheck-up, or have access to one." n
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