. Opponents' commentaries on the elaboration and modification of classification criteria are successively considered and commented; much attention is given to the problem of terminology.

We examined the distribution of non-B27 alleles of the HLA-B locus among B27+ patients with ankylosing spondylitis (AS), to detect any additional HLA-B locus allele(s) that may act in conjunction with B27 to increase susceptibility to AS. HLA-Bw60 (or B40 when the Bw60,61 split of B40 was not typed for) was shown to be increased among B27+ AS patients in each of 5 independent data sets. This increase was statistically significant in 4 of the 5 data sets studied, and the overall significance was P < 0.00001. Susceptibility to AS in

The present study was performed on 61 HLA-B27 positive first-degree relatives and 40 HLA-B27 negative relatives of 20 HLA-B27 positive probands with ankylosing spondylitis (AS). Of 24 HLA-B27 positive relatives 45 years or older, 21% had AS and 38% sacroiliitis. The HLA-B27 negative relatives did not have features of either disease. In the population study of 2,957 individuals 45 years or older, we found 5 cases of HLA-B27 positive sacroiliitis (according to the New York criteria) and 3 of these fulfilled the New York criteria for diagnosis of AS. In 2 of these 3 individuals, the diagnosis was made on clinical grounds. The phenotype frequency of HLA-B27 in this population is 7.8%, or about 230 HLA-B27 positive individuals in this population sample. Since AS was found in only 3 individuals, 1.3% of the HLA-B27 positive individuals in the population at large have AS; therefore, our data show that among individuals 45 years or older, 21% of HLA-B27 positive relatives of HLA-B27 positive AS patients have AS as compared with 1.3% of the HLA-B27 positive individuals in the population at large. Thus, the risk for AS is 16 times greater in the HLA-B27 positive relatives compared with HLA-B27 positive individuals in the population at large. The discriminatory value of the New York criterion of history of pain or the presence of pain at the dorsolumbar junction or in the lumbar spine was analyzed in the population and family studies and was found to be too nonspecific.

A past history of clinical Lyme borreliosis and the 6-month incidence of clinical and asymptomatic Lyme borreliosis was studied prospectively in a high-risk population. In the spring, blood samples were drawn from 950 Swiss orienteers, who also answered a questionnaire. IgG antiBorrelia burgdorferi antibodies were detected by ELISA. Positive IgG antibodies were seen in 248 (26.1%), in contrast to 3.9%-6.0% in two groups of controls (n = 101). Of the orienteers, 1.9%-3.1% had a past history of definite or probable clinical Lyme borreliosis. Six months later a second blood sample was obtained from 755 participants, 558 (73.9%) of whom were seronegative initially; 45 (8.1%) had seroconverted from negative to positive. Only 1 (2.2%) developed clinical Lyme borreliosis, Among all participants, the 6-month incidence of clinical Lyme borreliosis was 0.8% (6/755) but was much higher (8.1%) for asymptomatic seroconversion (45/558). In conclusion, positive Lyme serology was common in Swiss orienteers, but clinical disease occurred infrequently.Lyme disease, now often called Lyme borreliosis (LB), may affect the skin, heart, joints, and nervous system [1][2][3][4][5][6]. Neurologic, cardiologic, and rheumatologic manifestations such as meningoencephalitis, neuropathy, atrioventricular nodal block, myocarditis, and arthritis may follow in a few weeks to months after erythema migrans (EM). This skin lesion, although characteristic, is by no means an obligatory sign of LB; it was found in only 41%-61% of patients with the disease [7,8]. Arthritis typically is oligoarticular and recurrent but may become chronic and erosive; it predominantly involves the knee joints [3,9].LB is caused by the bite of ticks infected with the spirochete Borrelia burgdorferi [10,11]. The ticks that can transmit disease are part of the Ixodes ricinus complex. The discovery of the spirochete led to serology as an aid in establishing the diagnosis of LB, especially in the absence of EM [12]. In Europe the disorder seems to have a wide and constant distribution [13]. In contrast, in the United States LB may have been confined to three enzootic areas (northeast coast, midwest, California), but cases appear to be increasing and infection to be spreading to new areas. Recognition may also account for some of the apparent increase. LB has now been reported from 35 states. In Long Island, New York, the incidence ofLB was found to be considerably higher than previously recognized [14].Some patients showed inapparent seroconversion after infection. The estimated ratio of apparent to inapparent infection was 1:1 in a study in Great Island, Massachusetts [8].To assess the usefulness of Lyme serology as a diagnostic tool, it would be important to know not only the sensitivity and specificity of the test but also its predictive value. This would imply knowledge about the prevalence and incidence of clinical LB and the ratio of apparent to inapparent infections in populations where the test is applied.We studied past history of clinical LB and frequency of positiv...