Table 1 Characteristics of the two studies and results of their analysis
From: Assessing agreement between malaria slide density readings
First author of study | Drakeley[29] | Ngasala[30] |
|---|---|---|
Objective of study | evaluation of associations between parasite prevalence, altitude and rainfall | evaluation of training in clinical and microscopical diagnosis |
Location | two regions of north-eastern Tanzania | two coastal districts north of Dar es Salaam Tanzania, |
Study design | population based cross-sectional surveys along altitude transects in those aged up to 45 years | cluster-randomized trial with slides taken from febrile children aged under five years presenting to primary health care (PHC) facilities |
Total number of paired readings in dataset | 1,601 | 973 |
Number of double-zero pairs excluded | 37 | 345 |
Number of pairs excluded due to missing readings | 0 | 39 |
Number of pairs excluded due to semi-quantitative readings | 0 | 61 |
Numbers of paired readings analysed | 1,564 | 528 |
Mean difference in square root counts (95% confidence interval, p value) | (not done because the dataset did not identify individual readers) | -1.51 (-2.1 to -0.95, p < 0.0001), with central laboratory tending to read higher than PHC |
95% limits of agreement in terms of square root counts, i.e. 2.5 and 97.5 percentiles (ideal limits are -1.39 to +1.39) | -5.3 to +4.7 | 15.2 to +9.2 |
95% limits of agreements in parasites/μl at average density of 2,000 parasites/μl (ideal limits are ± 780 parasites/μl) | -2,800 to +2,500 | 8,600 to +5,200/μl |
95% limits of agreements in terms of parasites/μl at average density of 10,000 parasites/μl (ideal limits are ± 1,800) | -6,200 to +5,700 | -19,200 to +11,700 |