• GONORRHOEA
• LABORATORY METHODS
• MICROBIOLOGY

There are differences of opinion as to the value of cultures in the diagnosis of gonorrhoea. Personally I think them indispensable in the case of women…1

For most of this Journal's existence laboratory culture of Neisseria gonorrhoeae provided definitive identification. However, even at its apogee, a single culture lacked 100% sensitivity. Multiple sampling, from multiple sites, was necessary to diagnose, to exclude and to assess advances in culture's efficiency.

Today, gonococcal nucleic acid amplification tests (NAATs) have their own sensitivity and specificity compared (invariably favourably) with ‘culture’, whose published details may lack data on sample-handling, transport and quality control.

Duncan Catterall's 1970 article2 highlights sharp contrasts with today's practice, procedures and prevalence:A full physical examination was performed on all the patients.Every patient had at least 4 pelvic examinations and the majority had 6 or more genital tests.gonococci were found in 31.6%They were all observed for at least 3 months.…even with a first-class cultural service, repeated examinations are needed to establish the diagnosis of gonorrhoea in womengonococci were found [by microscopy] in only 67 (69%) of 95 consecutive cases

This last quote demonstrates how ‘a poor culture service flatters the microscopist’. Catterall used McLeod's culture medium and diagnosed 60% of gonorrhoea at the first visit. Other Centres reported figures between 88% and 95%. At St Thomas's, the use of Ian Phillips' VCNT (Vancomycin, Colistin, Nystatin and Trimethoprim) combined with scrupulous attention to detail, improved this to 98% by 1978 (St Thomas' Hospital microscopy had 50% success compared with Catterall's 69%).

When you next read of a commercial test's superiority, consider whether the culture was as good as the best of the 1970s.

Thoughts for the 21st century:

• A poor culture service flatters the microscopist NAAT.

• Epidemiological treatment precludes repeated culture/comparative analysis.

• ‘Culture’ sensitivity may vary in 2017 as it did in the 1970s.