Summary Since the season of summer hay fever may last only 4 weeks and rainfall may produce days with virtually no airborne pollen, the timing of clinical trials is important. To facilitate this a method of forecasting the first possible 100% symptom day, and the severity of the season in terms of light, moderate or severe, is presented. The forecast is based on temperature in April and May, and formulae tested by reference to records of grass pollen concentrations over Central London during 1961–70.

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SYNOPSISThe value of direct microscopy and cultural tests in onychomycosis is reported on the results of the examination of 3,955 nail collections from patients infected with Trichophyton rubrum. Of the total number of mycological diagnoses, 15 % would have been missed if culture had been omitted and 53 % if direct microscopy had not been undertaken. METHODSIn the mycological diagnosis of onychomycosis tissue may be examined either by culture or by the so-called direct method, in which nail parings, after hydrolysis in potassium hydroxide solution, are squashed to a more or less unicellular layer and then searched microscopically for the presence of hyphae or mycelium. In some laboratories direct examination is performed only when no fungi have been grown within a period varying from three to six weeks from the planting of the nail in agar media; in others culture is undertaken only when direct examination has shown fungus to be present, and there are yet other laboratories performing both tests for every specimen.In our routine for the investigation of nail parings, three or four pieces are examined in 30% KOH, three are planted in peptone glucose agar containing 40 utg/ml chloramphenicol, and six in malt extract agar containing 40 zg/ml chloramphenicol and 0 5 mg/ml of cycloheximide. All cultures are incubated at 25'C for six weeks before any are discarded as negative. No direct preparation is recorded as negative until it has been searched for a minimum of ten minutes unless the amount of material is inadequate.This paper reports an analysis of the results of examining 3,955 samples of nails from patients with Trichophyton rubrum infections during a therapeutic trial of griseofulvin (Davies, Everall, and Hamilton, 1967). Table I shows the relative numbers of mycological diagnoses by direct microscopy, culture, or both. RESULTSOnly 913 (46%) of the nails judged to be infected by such clinical criteria as hyperkeratosis and discoloration showed fungus by microscopy or culture or both (Table I). Had greater care been taken in collection and a greater amount tested from each Received for publication 21 March 1968. nail, the figure might have been higher, but fungi are not the sole cause of nail dystrophy. On the other hand it is noteworthy that 170 (9 %) of the normal, healthy looking nails from infected patients showed fungus by one or other method. Of 2,001 nails regarded as infected by the clinician, 803 (40%) showed fungus by direct microscopy but in only 313 (39%) of these was T. rubrum isolated. The difficulty in isolating fungus from nails is well recognized (Walshe and English, 1966)

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