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Table 2 Summary of findings on benefit outcomes for screening versus no screening (key question 1)

From: Screening for chlamydia and/or gonorrhea in primary health care: systematic reviews on effectiveness and patient preferences

Outcome Study approach Assumed population riska Studies; sample sizeb Follow-up (yrs) Absolute effects Certaintyc What happens?
PID
MID 2.5 fewer or more per 1000
Offer of universal CT screening, annually for 1–3 years Study data 2 RCTs; 141,362 [8, 59] 1–3 0.1 more in 1000 (2.1 fewer to 1.5 more) Low to moderate Little-to-no difference
General 0.3 more in 1000 (7.6 fewer to 11 more) Very low Little-to-no difference
High 0.5 more in 1000 (13.1 fewer to 18.7 more) Very low Little-to-no difference
Offer of 1 universal CT screen—selected population Study data 1 RCT; 2607 [108] 1 11.8 fewer per 1000 (2.3 to 16.3 fewer) Low to moderate Small reduction
General 15.4 fewer per 1000 (3 to 21.3 fewer) Low to moderate Small reduction
High 26.8 fewer per 1000 (5.2 to 37.1 fewer) Low Moderate reduction
Acceptors of 1 universal CT screen Study data 2 RCTs [28, 105], 1 CCT [88]; 30,652 1 3.7 fewer per 1000 (7.1 fewer to 0.7 more) Low Small reduction
General 5.7 fewer per 1000 (10.8 fewer to 1.1 more) Low Small reduction
High 9.9 fewer per 1000 (18.8 fewer to 1.9 more) Very low to low Moderate reduction
Ectopic pregnancy
MID 1 fewer or more per 1000
Offer of 1 universal CT screen General 1 RCT; 15,459 [59] 9 0.20 more per 1000 (2.2 fewer to 3.9 more) Very low Little-to-no difference
Acceptors of 1 universal CT screen High 1 CCT; 28,074 [88] 1.5 0.63 more per 1000 (0.76 fewer to 2.8 more) Very low Little-to-no difference
Infertility—female
MID 1 fewer or more per 1000
Offer of 1 universal CT screen General 1 RCT; 15,459 [59] 9 4.2 more per 1000 (1.7 fewer to 11.2 more) Very low Very uncertain
Acceptors of 1 universal CT screen High 1 CCT; 28,074 [88] 1.5 0.15 fewer per 1000 (0.37 fewer to 0.88 more) Very low Very uncertain
Transmission of CT—prevalence
MID 5 and 10 fewer or more per 1000
Offer of universal CT screening—annually for 1–3 years General—both sexes 3 cluster RCTs; 41,709 [8, 9, 12] 1–3 3 fewer per 1000 (11.5 fewer to 6.9 more) Low (5 fewer per 1000)
Low to moderate (10 fewer per 1000)
Little to no difference
General— females 2 cluster RCTs; 27,300 [8, 9] 2–3 4.1 fewer (13.5 fewer to 9.75 more) Very low to low (5 fewer per 1000)
Low (10 fewer per 1000)
Little-to-no difference
General— males 2 cluster RCTs; 11,749 [8, 9] 2-3 7.2 fewer (18.9 fewer to 8.6 more) Very low (5 fewer per 1000)
Very low to low (10 fewer per 1000)
Very uncertain
Offer of universal CT and NG screening—frequent screening over 2.5–4 years High—both sexes 1 cluster CCT; 3803 [89] 2.5 26 fewer cases in 1000 (65 fewer to 68 more) Very low (both thresholds) Very uncertain
High—females 1 RCT [60]; 1 CCT [89]; 6127 2.5–4 34.3 fewer per 1000 (4 to 58 fewer); NNS 29 (17 to 250) Low to moderate (both thresholds) Moderate reduction
High—males 1 CCT; 1830 [89] 2.5 31 fewer per 1000 (55 fewer to 52 more) Very low (both thresholds) Very uncertain
Transmission of NG—prevalence
MID 5 and 10 fewer or more per 1000
Offer of universal CT and NG screening—frequent screening over 2.5–4 years High—both sexes 1 CCT; 3765 [89] 2.5 3 fewer in 1000 (5 fewer to 87 more) Very low Very uncertain
High—females 1 RCT [60], 1 CCT [89]; 6000 2.5–4 5–7 fewer per 1000 Very low to low Moderate reduction
High—males 1 CCT; 1826 [89] 2.5 0.4 fewer in 1000 (10 fewer to 117 more) Very low Very uncertain
  1. Abbreviations: CCT controlled clinical trial, CT Chlamydia trachomatis, MID minimally important difference threshold, NG Neisseria gonorrhoeae, NNS number needed to screen, RCT randomized controlled trial, RR relative risks
  2. a For PID, the absolute effects and certainty assessment the in Study Data rows used the control event rates from the studies, applying the median value when more than one study contributed to the analysis. The general-risk and high-risk assumed population risk estimates were calculated using the relative effects (RR) from the studies together with an estimate of the risk without screening, based on the natural history parameters of CT (see Additional files 3 and 6). The studies reporting on PID enrolled samples considered to be at general risk. For the other outcomes, the (median) control event rate of the studies was used for the calculations, but the level of risk of the study population (general risk ≤7% vs. high risk >7% CT prevalence at baseline) is indicated
  3. b Sample sizes for the outcome of transmission are for those participants who had this outcome assessed (e.g., through surveys), not the number enrolled in the trials. All findings from observational studies are described in Additional file 6 and provided very low certainty evidence
  4. c Reasons for ratings are explained in Additional file 6