Evaluation and comparison of tests to diagnose Chlamydia trachomatis genital infections

Infection with Chlamydia trachomatis results in intracytoplasmic inclusionsand the generation of infectious elementary bodies (EBs). These can bedetected by various procedures. Staining of epithelial cells with vitaldyes was first used to detect inclusions, but is insensitive. Thus,Papanicolaou-stained cervical smears cannot be recommended. The advent ofthe ability to grow chlamydiae in cultured cells over 30 years ago had amajor impact on chlamydial research and on detection. However, thisprocedure is probably <70% sensitive for cervical infection and less forurethral infection in men and is now practised infrequently following theadvent of other, mostly less laborious and often equally, or more sensitivedetection systems. Thus, staining a smear with a specific fluorescentmonoclonal antibody to detect EBs is simple and the direct fluorescentantibody tests became a commercial proposition in the early to mid-1980s.Nevertheless, although highly sensitive and specific in competent hands,technical expertise is crucial and even the most experienced may be unableto read a large number of stained smears on slides quickly. In view ofthis, it is understandable that enzyme-linked immunosorbent assays (ELISAs)gained popularity from the mid-1980s onwards, for they are not very labourintensive and their reading is neither subjective nor tedious.Unfortunately, these aspects outweighed the fact that the ELISAs lacksensitivity, some being very insensitive. The situation has been rescued,however, by the advent in the early 1990s of methods that amplifychlamydial DNA, making it easily detectable by relatively simpleprocedures. The polymerase chain reaction is such a method and has highspecificity and sensitivity, although commercial development has so far notmet the high standard expected of it in terms of sensitivity. The ligasechain reaction does not invoke such criticism, and high values for bothsensitivity and specificity may be expected, even on urine samples. Thisaugers well for diagnosing an infected individual patient and for effectivescreening programmes. Antibody tests have no place in a screening programmeand are of debatable value in diagnosis.