In this article, we have discussed the basic knowledge to calculate sensitivity, specificity, positive predictive value and negative predictive value. We have discussed the advantage and limitations of these measures and have provided how we should use these measures in our day-to-day clinical practice. We also have illustrated how to calculate sensitivity and specificity while combining two tests and how to use these results for our patients in day-to-day practice.

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Aim: To report progression of primary angle closure suspects (PACS) to primary angle closure (PAC) at the 5 year follow up of a population based sample. Methods: 82 of 118 PACS who could be contacted and 110 randomly selected normals from a population based survey in 1995 were invited for a follow up examination in 2000. Progression to PAC was based on the development of raised IOP or synechiae in a PACS. Results: 50 of the 82 PACS contacted were examined. 11 (22%; 95% CI 9.8 to 34.2) developed PAC (seven synechial and four appositional); all were bilateral PACS. Two of 50 people previously diagnosed as PACS were reclassified as normal. One person among the 110 normals progressed to PAC. The relative risk of progression among PACS was 24 (95% CI 3.2 to 182.4). There was no significant difference in axial length, anterior chamber depth, or lens thickness between those who progressed and those who did not. None of the patients developed optic disc or field damage attributable to angle closure. One angle closure suspect was diagnosed to have normotensive glaucoma. Conclusion: In this population based study of PACS the 5 year incidence of PAC was 22%; none developed functional damage. Bilateral PACS was a clinical risk factor for progression.

ABSTRACT.Objective: To report the 5-year progression to primary angle closure glaucoma (PACG) in a population-based cohort of primary angle closure (PAC) subjects. Methods: A total of 37 patients diagnosed as PAC during a population-based study in 1995 were invited for re-examination in 2000. Patients underwent a complete ophthalmic examination including ocular biometry. Progression to PACG was based on optic disc damage and field defects on automated perimetry. Results: In all, 28 of 32 PAC subjects who could be contacted presented for examination. Eight (28.5%; 95% CI 12-45%) had progressed to PACG; two of seven with appositional and six of 21 with synechial closure. All were advised laser peripheral iridotomy (LPI) in 1995; one of the nine who underwent LPI progressed compared to seven of 19 who refused LPI. Four of those originally diagnosed with appositional closure developed peripheral anterior synechiae. One eye of a person previously diagnosed with appositional PAC was reclassified as a primary angle closure suspect (PACS). There was no significant difference in biometric parameters between those who progressed and those who did not. None developed acute PACG or blindness due to glaucoma. Conclusion: In this population-based study of primary angle closure, the 5-year incidence of PACG was eight patients (28.5%; 95% CI 12-45%). We were unable to identify any features that predicted progression.

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In this article we provide an introduction to the use of likelihood ratios in clinical ophthalmology. Likelihood ratios permit the best use of clinical test results to establish diagnoses for the individual patient. Examples and step-by-step calculations demonstrate the estimation of pretest probability, pretest odds, and calculation of posttest odds and posttest probability using likelihood ratios. The benefits and limitations of this approach are discussed.

The strong association of specific haplotypes with some predominant CYP1B1 mutations underlying PCG and the observed geographical clustering, probably due to founder effects, may be useful for predictive testing.

The present study indicates a limited role of FOXC1 in PCG pathogenesis.